Rails - May 2006 - MissingSourceFile (no such file to load -- breakpoint):

Anyone seen this before? I did a gem update recently and may have broken 
something. But I''d still like to decipher what the message below 
actuallt means:

MissingSourceFile (no such file to load -- breakpoint):
     /usr/lib64/site_ruby/1.8/rubygems/custom_require.rb:21:in
`require__''
     /usr/lib64/site_ruby/1.8/rubygems/custom_require.rb:21:in
`require''
 
/usr/lib64/ruby/gems/1.8/gems/activesupport-1.3.0/lib/active_support/dependencies.rb:136:in
`require''
     /usr/lib64/ruby/gems/1.8/gems/rails-1.1.0/lib/dispatcher.rb:80:in 
`prepare_breakpoint''
     /usr/lib64/ruby/gems/1.8/gems/rails-1.1.0/lib/dispatcher.rb:68:in 
`prepare_application''
     /usr/lib64/ruby/gems/1.8/gems/rails-1.1.0/lib/dispatcher.rb:37:in 
`dispatch''
 
/usr/lib64/ruby/gems/1.8/gems/mongrel-0.3.12.4/lib/mongrel/rails.rb:66:in 
`process''
     /usr/lib64/ruby/1.8/thread.rb:135:in `synchronize''
 
/usr/lib64/ruby/gems/1.8/gems/mongrel-0.3.12.4/lib/mongrel/rails.rb:64:in 
`process''
 
/usr/lib64/ruby/gems/1.8/gems/mongrel-0.3.12.4/lib/mongrel.rb:425:in 
`process_client''
 
/usr/lib64/ruby/gems/1.8/gems/mongrel-0.3.12.4/lib/mongrel.rb:424:in 
`process_client''