Is just got Mongrel working with Rails 2.0.2 and RubyGems 1.0.1 on Windows.

What I did was to delete all prior Versions of Mongrel except Version 1.1.3

You can use the command gem uninstall mongrel ( Select the Versions prior to 1.1.3 and delete them, then 1.1.3 will be used by default)