Error when running migrations

I’ve checked out a rails project that i’m working on from a repository,
and created a new database for it. However whenever i try and run the
migrations i get the following error:

rake aborted!
#AppConfig:0xb7870f84 is not a class/module

Whenever I try to fire up a webrick server, i get the following error:

=> Booting WEBrick…
/usr/local/lib/ruby/site_ruby/1.8/rubygems.rb:274:in activate': #<AppConfig:0xb7342918> is not a class/module (TypeError) from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:inrequire’
from
/usr/local/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:495:in
require' from /usr/local/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:342:innew_constants_in’
from
/usr/local/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:495:in
require' from script/../config/../vendor/plugins/validates_captcha/init.rb:11:inload_plugin’
from
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/initializer.rb:401:in
load_plugin' from /usr/local/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/core_ext/kernel/reporting.rb:11:insilence_warnings’
from
/usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/initializer.rb:401:in
load_plugin' ... 18 levels... from /usr/local/lib/ruby/gems/1.8/gems/rails-1.2.3/lib/commands/server.rb:39 from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:ingem_original_require’
from
/usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:27:in
`require’
from ./script/server:3

I’m not quite sure as to how to debug this type of thing. I’m running
ubuntu 7.04, and my ruby version information is as follows: ruby 1.8.6
(2007-03-13 patchlevel 0) [i686-linux]

According to the other developers on the project, they can check it out
with the same configuration and run the migration just fine. Also - this
works perfectly fine on my windows desktop (running migrations and
starting the server), so that’s pretty weird. Is there something wrong
with my ruby configuration?

Any help on this problem would be appreciated.