so my experience with rails 3.1 rc and jruby is the following so far:
first fix was the template you use with jruby
https://github.com/jruby/jruby-rails-templates/commit/7d8f3bd518bfd3cf82958b0d6ca7659cc0626c27
then the webrick server started !
what I did is summarized in
https://gist.github.com/1018786#file_gistfile1.txt
which basically new rails application, scaffolded a resource, migrated
the DB and the started the server.
first issue
