Bulk updating Gem source index for: http://gems.rubyforge.org

Hi all,

I'm having a bit of a problem with installing ruby on rails using gem on Windows XP. after gem install rails --include-dependencies it say as follows

Bulk updating Gem source index for: http://gems.rubyforge.org ERROR: While executing gem ... (Gem::InstallError)     invalid gem format for c:/ruby/lib/ruby/gems/1.8/cache/ actionpack-1.13.3.gem

Any idea what I'm doing wrong here?