Cannot install plugins

I used to be able to install plugins, but for some reason the plugins system has stopped working for me.

If I try to install something like comatose, I get the following:

C:\rails\BAct>ruby script/plugin source http://mattmccray.com/svn/rails/plugins
c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:422:in `remove_const': cannot remove Object::OPT_TABLE (NameError)
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:422:in `send'
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:422:in `remove_constant'
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:368:in `new_constants_in'
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:368:in `each'
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:368:in `new_constants_in'
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.4.2/lib/active_support/dependencies.rb:495:in `require'
        from script/plugin:3

I get the same set of errors (exactly) for almost any plugins command I try.

I am using Windows XP, rails 1.2.3, and have updated all of my gems.

Anybody know what I am doing wrong, or how to fix this?

-- Will Merrell