Following is the error i receive while running test cases written using rpsec. The strange thing is the test were running fine until early yesterday. Can someone guide me towards a solution. I am new to RSpec and and using Rspec and rspec-rails as plugins in my app. and i have no clue to what went wrong.

F:/Spritle/programs/ruby 1.86/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_suppor
    t/dependencies.rb:105:in `const_missing': uninitialized constant Test::Unit::TestResult::TestResultFailureSupport (NameError)
            from F:/Spritle/programs/ruby 1.86/lib/ruby/gems/1.8/gems/test-unit-2.0.1/lib/test/unit/testresult.rb:28
            from F:/Spritle/programs/ruby 1.86/lib/ruby/site_ruby/1.8/rubygems/custom_require.
    rb:31:in `gem_original_require'
            from F:/Spritle/programs/ruby 1.86/lib/ruby/site_ruby/1.8/rubygems/custom_require.
    rb:31:in `require'
            from F:/Spritle/programs/ruby 1.86/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/
    active_support/dependencies.rb:158:in `require'
            from F:/Spritle/projects/Evaluation/vendor/plugins/rspec/lib/spec/interop/test.rb:
    34
            from F:/Spritle/programs/ruby 1.86/lib/ruby/site_ruby/1.8/rubygems/custom_require.
    rb:31:in `gem_original_require'
            from F:/Spritle/programs/ruby 1.86/lib/ruby/site_ruby/1.8/rubygems/custom_require.
    rb:31:in `require'
            from F:/Spritle/programs/ruby 1.86/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/
    active_support/dependencies.rb:158:in `require'
             ... 15 levels...
            from F:/Spritle/projects/Evaluation/vendor/plugins/rspec/lib/spec/runner/example_g
    roup_runner.rb:14:in `load_files'
            from F:/Spritle/projects/Evaluation/vendor/plugins/rspec/lib/spec/runner/options.r
    b:133:in `run_examples'
            from F:/Spritle/projects/Evaluation/vendor/plugins/rspec/lib/spec/runner/command_l
    ine.rb:9:in `run'
            from F:/Spritle/projects/Evaluation/vendor/plugins/rspec/bin/spec:5
    rake aborted!
    Command "F:/Spritle/programs/ruby 1.86/bin/ruby.exe" -I"lib"  "F:/Spritle/projects/Evaluation/vendor/plugins/rspec/bin/spec" "spec/controllers/articles_controller_spec.rb" --option
    s "F:/Spritle/projects/Evaluation/spec/spec.opts" failed