If you don’t use gemsets, this can occur to you. Although I do use gemsets almost always I had a ruby project running on the rvm 1.9.2 with messed up gems, many versions of each one etc. Anyway I decided I want to cleanup all the gems that are installed under this ruby.
The most practical way to delete all gems and all versions that I run into is the following
gem list | cut -d" " -f1 | xargs gem uninstall -aIx
It works! Just try it out..