Unknown encoding error on running rake - ruby-on-rails

Question

I have been writing a Rails app and only now started bringing it under
test coverage. I have written a basic test and when I execute the
'rake' command at the command prompt, I get the following errors:
E:\testapp>rake
(in E:/testapp)
E:/Ruby192/bin/ruby.exe: unknown encoding name - \Ruby192\lib
(RuntimeError)
E:/Ruby192/bin/ruby.exe: unknown encoding name - \Ruby192\lib
(RuntimeError)
E:/Ruby192/bin/ruby.exe: unknown encoding name - \Ruby192\lib
(RuntimeError)
Errors running test:units, test:functionals, test:integration!
When I run rake test:units, I get
E:\testapp>rake test:units
(in E:/testapp)
E:/Ruby192/bin/ruby.exe: unknown encoding name - \Ruby192\lib
(RuntimeError)
rake aborted!
Command failed with status (1): [E:/Ruby192/bin/ruby.exe -I"lib;test"
"E:/R...]
E:/Ruby192/lib/ruby/1.9.1/rake.rb:993:in `block in sh'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1008:in `call'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1008:in `sh'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1092:in `sh'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1027:in `ruby'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1092:in `ruby'
E:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.5/lib/rails/test_unit/testing.rake:26:in `block (2 levels) in define'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1110:in `verbose'
E:/Ruby192/lib/ruby/gems/1.9.1/gems/railties-3.0.5/lib/rails/test_unit/testing.rake:11:in `block in define'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:634:in `call'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:634:in `block in execute'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:629:in `each'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:629:in `execute'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:595:in `block ininvoke_with_call_chain'
E:/Ruby192/lib/ruby/1.9.1/monitor.rb:201:in `mon_synchronize'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:588:in `invoke_with_call_chain'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:581:in `invoke'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:2041:in `invoke_task'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:2019:in `block (2 levels) intop_level'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:2019:in `each'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:2019:in `block in top_level'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:2058:in`standard_exception_handling'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:2013:in `top_level'
E:/Ruby192/lib/ruby/1.9.1/rake.rb:1992:in `run'
E:/Ruby192/bin/rake:31:in `<main>'
I have tried searching on the Net to no success.. I initially assumed
something was wrong with my test code, but I get the same errors with
a new rails app!!
I am using Rails 3.0.5 on Ruby 1.9.2p180 on Windows Vista. On a friend's suggestion, I
installed RubyInstaller and used DevKit, but I still get the same
error.
Any inputs?

Answer 1

Looking at the path it seems you are pointing to ruby 1.9.1
E:/Ruby192/lib/ruby/1.9.1/rake.rb
I'm not familiar with Windows but something must still be pointing at the old Ruby version