i get the above error, all i did was install rvm and update to ruby 1.9.2 from the default ruby that you get with mac.
all my gems appear in the gem list but do i ne
Check that you have the gems installed gem list If not, install as usual gem install whatever or if you want a specific version gem install whatever -v 1.2.3 Or if you have bundler in your project (ie Rails), it's just bundle install
If you have all the gems, then this is probably a local file, and you're probably coming from Ruby version < 1.9, you need to either fix your $LOAD_PATH (which will depend on too many factors for me to explain here), or specify the full path to the file you want File.dirname(__FILE__) + '/myapp'
Otherwise, you need to give more info, like what version you used to be running, what myapp is, and where it is in relation to your file.