Like this post I am also trying to complete this heroku tutorial

I have installed and used everything (node.js, npm, express) successfully until I got to Foreman. I installed Foreman by first installing Ruby:

alex@ubuntu:~$ sudo apt-get install ruby1.9.1

then installing Foreman. I am a newbie to Unix so I "sudo" perhaps unnecessarily here, but I got confirmation in the terminal that it had installed but also some errors:

alex@ubuntu:~/NodeHelloWorld$ sudo gem install foreman
Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z"
Successfully installed term-ansicolor-1.0.7
Successfully installed foreman-0.26.1

Then when I try to start foreman I get similar:

alex@ubuntu:~/NodeHelloWorld$ foreman start
Invalid gemspec in [/var/lib/gems/1.8/specifications/foreman-0.26.1.gemspec]: invalid date format in specification: "2011-11-10 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/term-ansicolor-1.0.7.gemspec]: invalid date format in specification: "2011-10-13 00:00:00.000000000Z"
/usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:926:in `report_activate_error': Could not find RubyGem foreman (>= 0) (Gem::LoadError)
    from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:244:in `activate_dep'
    from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:236:in `activate'
    from /usr/lib/ruby/vendor_ruby/1.8/rubygems.rb:1307:in `gem'
    from /usr/local/bin/foreman:18

Can anyone help me? I am a newbie to Unix after finally dumping windows as I found I could not get foreman-windows to work for me either

I have found this post from someone with apparently the same issue. Does this mean my version of ruby could be wrong? I am running 1.9.1, though again new to ruby as well;

alex@ubuntu:~/NodeHelloWorld$ ruby1.9.1 -v
ruby 1.9.2p290 (2011-07-09 revision 32553) [i686-linux]

Thanks