Tiago,
Why don't you just freeze the version of rails you were using into the /vendor directory? That way you can still use the existing application and plugins as they are.
The usual call is 'rake freeze_gems'
BR
Mezza
Hi Tiago,
I usually run the rake freeze_gems or rake rails:freeze:gems on my apps on my development box before pushing them up to production servers.
If you can't do that for whatever reason, it is also possible to svn external a link in your /vendor directory.
I don't do this too much, so not sure of the syntax, but I'm sure you'll be able to google it. The Rails 1.1 release should be able to be svn externalled into your app by typing:
svn propset svn:externals "rails http://dev.rubyonrails.org/svn/rails/branches/1-1-stable" vendor
from the root of your rails app. Assuming your on *nix and have svn available.
There is also one last option which is that if your hosting company haven't deleted the previous versions of the rails gems you cold edit your environment.rb file to specify the version you want to use (but I'd stick with just freezing the version you want to /vendor).
HTH
Mezza