Webrick Server don't start after Update Rails

After a Rails update (rails-1.1.6) , Webrick server don't start.

Error:   Cannot find gem for Rails =1.1.4:

<...>

  -> How can I best solve the problem for the old projects:           Starting a new project and copy the files?

Go to your application config/ folder and edit environment.rb. There should be line RAILS_GEM_VERSION = '1.1.4'. Change it to match current Rails version.

Regards, Rimantas