no such file to load -- uuid (MissingSourceFile)

Hi there,

I was trying to use both Ruby 1.8.6 and Ruby 1.9.1 on my laptop.

After I install Ruby 1.9.1, I went back to my Ruby 1.8.6, and run :
Ruby script/server. I got the following error:

/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/
1.8/rubygems/custom_require.rb:27:in `gem_original_require': no such
file to load -- uuid (MissingSourceFile)

Maybe it could not fine the file, how can I fix this?

Thank you very much!