I've been banging my head against the wall for the better part of an hour trying to figure out what's going wrong here, and I'm sure (or rather hoping) it's something fairly obvious that I'm overlooking. I'm using Ruby 1.9.1, Sinatra 1.0, and RMagick 2.13.1. ImageMagick and RMagick are correctly installed and functional—I've successfully manipulated and saved images from irb.

The relevant part of the params array (formatting changes for the sake of readability):

{"admin_user_new_image_file"=>
    {
        :filename=>"freddie-on-shetland-pony.png",
        :type=>"image/png", 
        :name=>"admin_user_new_image_file", 
        :tempfile=>#<File:/var/folders/a7/a7pO5jMcGLCww9XBGRvWfE+++TI/-Tmp-/RackMultipart20100514-20700-o2tkqu-0>,
        :head=>"Content-Disposition: form-data; name=\"admin_user_new_image_file\"; filename=\"freddie-on-shetland-pony.png\"\r\nContent-Type: image/png\r\n"
    }
}

The relevant code:

post "/admin/user/:account_name/image/new/" do
  if params[:admin_user_new_image_file][:tempfile]
    thumbnail = Magick::Image.read("png:"+params[:admin_user_new_image_file][:tempfile].path).first
  end
end

The error (line 229 is the line starting with "thumbnail = ":

config.ru:229: [BUG] Segmentation fault
ruby 1.9.1p376 (2009-12-07 revision 26041) [i386-darwin10.3.0]

-- control frame ----------
c:0042 p:---- s:0196 b:0196 l:000195 d:000195 CFUNC  :read
c:0041 p:0121 s:0192 b:0192 l:001ab8 d:000191 LAMBDA config.ru:229
c:0040 p:---- s:0189 b:0189 l:000188 d:000188 FINISH
c:0039 p:---- s:0187 b:0187 l:000186 d:000186 CFUNC  :call
c:0038 p:0018 s:0184 b:0184 l:001d78 d:000183 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:865
c:0037 p:---- s:0182 b:0182 l:000181 d:000181 FINISH
c:0036 p:---- s:0180 b:0180 l:000179 d:000179 CFUNC  :instance_eval
c:0035 p:0016 s:0177 b:0175 l:000174 d:000174 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:521
c:0034 p:0024 s:0171 b:0171 l:000148 d:000170 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:500
c:0033 p:---- s:0169 b:0169 l:000168 d:000168 FINISH
c:0032 p:---- s:0167 b:0167 l:000166 d:000166 CFUNC  :catch
c:0031 p:0140 s:0163 b:0163 l:000148 d:000162 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:497
c:0030 p:---- s:0154 b:0154 l:000153 d:000153 FINISH
c:0029 p:---- s:0152 b:0152 l:000151 d:000151 CFUNC  :each
c:0028 p:0073 s:0149 b:0149 l:000148 d:000148 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:476
c:0027 p:0076 s:0141 b:0141 l:000140 d:000140 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:601
c:0026 p:0009 s:0137 b:0137 l:000138 d:000136 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411
c:0025 p:---- s:0135 b:0135 l:000134 d:000134 FINISH
c:0024 p:---- s:0133 b:0133 l:000132 d:000132 CFUNC  :instance_eval
c:0023 p:0012 s:0130 b:0130 l:000121 d:000129 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566
c:0022 p:---- s:0128 b:0128 l:000127 d:000127 FINISH
c:0021 p:---- s:0126 b:0126 l:000125 d:000125 CFUNC  :catch
c:0020 p:0013 s:0122 b:0122 l:000121 d:000121 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566
c:0019 p:0098 s:0115 b:0115 l:000138 d:000138 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411
c:0018 p:0019 s:0108 b:0108 l:000107 d:000107 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:399
c:0017 p:0014 s:0104 b:0104 l:000103 d:000103 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24
c:0016 p:0150 s:0098 b:0098 l:000097 d:000097 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/methodoverride.rb:24
c:0015 p:0031 s:0092 b:0092 l:000091 d:000091 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18
c:0014 p:0018 s:0084 b:0084 l:002080 d:000083 BLOCK  /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979
c:0013 p:0032 s:0082 b:0082 l:000081 d:000081 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:1005
c:0012 p:0011 s:0078 b:0078 l:002080 d:002080 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979
c:0011 p:0100 s:0074 b:0074 l:000ff0 d:000ff0 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:47
c:0010 p:0022 s:0068 b:0068 l:000067 d:000067 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:35
c:0009 p:0014 s:0064 b:0064 l:000063 d:000063 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24
c:0008 p:0031 s:0058 b:0058 l:000057 d:000057 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18
c:0007 p:0014 s:0050 b:0050 l:000049 d:000049 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/content_length.rb:13
c:0006 p:0320 s:0042 b:0042 l:000041 d:000041 METHOD /usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/handler/webrick.rb:48
c:0005 p:0256 s:0030 b:0030 l:000029 d:000029 METHOD /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:111
c:0004 p:0382 s:0020 b:0020 l:000019 d:000019 METHOD /usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:70
c:0003 p:0123 s:0009 b:0009 l:000bc8 d:000008 BLOCK  /usr/local/lib/ruby/1.9.1/webrick/server.rb:183
c:0002 p:---- s:0004 b:0004 l:000003 d:000003 FINISH
c:0001 p:---- s:0002 b:0002 l:000001 d:000001 TOP   
---------------------------
-- Ruby level backtrace information-----------------------------------------
config.ru:229:in `read'
config.ru:229:in `block (2 levels) in <main>'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:865:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:865:in `block in route'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:521:in `instance_eval'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:521:in `route_eval'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:500:in `block (2 levels) in route!'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:497:in `catch'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:497:in `block in route!'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:476:in `each'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:476:in `route!'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:601:in `dispatch!'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411:in `block in call!'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `instance_eval'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `block in invoke'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `catch'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:566:in `invoke'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:411:in `call!'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:399:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/methodoverride.rb:24:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979:in `block in call'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:1005:in `synchronize'
/usr/local/lib/ruby/gems/1.9.1/gems/sinatra-1.0/lib/sinatra/base.rb:979:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:47:in `_call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/lint.rb:35:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/showexceptions.rb:24:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/commonlogger.rb:18:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/content_length.rb:13:in `call'
/usr/local/lib/ruby/gems/1.9.1/gems/rack-1.1.0/lib/rack/handler/webrick.rb:48:in `service'
/usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:111:in `service'
/usr/local/lib/ruby/1.9.1/webrick/httpserver.rb:70:in `run'
/usr/local/lib/ruby/1.9.1/webrick/server.rb:183:in `block in start_thread'

-- C level backtrace information -------------------------------------------
0x10010cd8d 0   libruby.dylib                       0x000000010010cd8d rb_vm_bugreport + 77
0x10002b184 1   libruby.dylib                       0x000000010002b184 report_bug + 260
0x10002b318 2   libruby.dylib                       0x000000010002b318 rb_bug + 200
0x1000b7124 3   libruby.dylib                       0x00000001000b7124 sigsegv + 132
0x7fff8301c80a 4   libSystem.B.dylib                   0x00007fff8301c80a _sigtramp + 26
0x1032313ac 5   libMagickCore.3.dylib               0x00000001032313ac Splay + 300
0x103119245 6   libMagickCore.3.dylib               0x0000000103119245 AcquirePixelCache + 325
0x1031cb317 7   libMagickCore.3.dylib               0x00000001031cb317 AcquireImage + 375
0x10333035b 8   libMagickCore.3.dylib               0x000000010333035b ReadPNGImage + 155
0x1031418fd 9   libMagickCore.3.dylib               0x00000001031418fd ReadImage + 2221
0x101f1b72b 10  RMagick2.bundle                     0x0000000101f1b72b rd_image + 339
0x101f1b59b 11  RMagick2.bundle                     0x0000000101f1b59b Image_read + 36
0x1000fd0e4 12  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 13  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 14  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 15  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x100106643 16  libruby.dylib                       0x0000000100106643 rb_vm_invoke_proc + 691
0x100106ccd 17  libruby.dylib                       0x0000000100106ccd vm_call0 + 1085
0x1000317c6 18  libruby.dylib                       0x00000001000317c6 rb_method_call + 406
0x1000fd0e4 19  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 20  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 21  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 22  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x100105ce6 23  libruby.dylib                       0x0000000100105ce6 yield_under + 710
0x100106188 24  libruby.dylib                       0x0000000100106188 specific_eval + 72
0x1000fd0e4 25  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 26  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 27  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 28  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x10010b6bf 29  libruby.dylib                       0x000000010010b6bf rb_f_catch + 639
0x1000fd0e4 30  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 31  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 32  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 33  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x10010aac9 34  libruby.dylib                       0x000000010010aac9 rb_yield + 505
0x100007902 35  libruby.dylib                       0x0000000100007902 rb_ary_each + 82
0x1000fd0e4 36  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 37  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 38  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 39  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x100105ce6 40  libruby.dylib                       0x0000000100105ce6 yield_under + 710
0x100106188 41  libruby.dylib                       0x0000000100106188 specific_eval + 72
0x1000fd0e4 42  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 43  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 44  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 45  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x10010b6bf 46  libruby.dylib                       0x000000010010b6bf rb_f_catch + 639
0x1000fd0e4 47  libruby.dylib                       0x00000001000fd0e4 vm_call_cfunc + 340
0x1000fe9b0 48  libruby.dylib                       0x00000001000fe9b0 vm_call_method + 896
0x1000ff8fc 49  libruby.dylib                       0x00000001000ff8fc vm_exec_core + 3180
0x100104b93 50  libruby.dylib                       0x0000000100104b93 vm_exec + 1203
0x100106643 51  libruby.dylib                       0x0000000100106643 rb_vm_invoke_proc + 691
0x100111803 52  libruby.dylib                       0x0000000100111803 thread_start_func_2 + 835
0x100111921 53  libruby.dylib                       0x0000000100111921 thread_start_func_1 + 17
0x7fff82ff58b6 54  libSystem.B.dylib                   0x00007fff82ff58b6 _pthread_start + 331
0x7fff82ff5769 55  libSystem.B.dylib                   0x00007fff82ff5769 thread_start + 13

[NOTE]
You may encounter a bug of Ruby interpreter. Bug reports are welcome.
For details: http://www.ruby-lang.org/bugreport.html

Abort trap

Anyone have any idea what's going on? Thanks!