from:http://stackoverflow.com/questions/25165016/cant-get-to-work-cocoapods-and-yosemite

In case someone else got the same issue, I did this to fix my issue:

1. Update Gems

   sudo gem update --system

   1	sudo gem update --system

2. Uninstalled xpreproj

   sudo gem uninstall xpreproj

   1	sudo gem uninstall xpreproj

3. Make sure to select All versions

4. Uninstalled Cocoapods

   sudo gem uninstall cocoapods

   1	sudo gem uninstall cocoapods

5. Install xpreproj

   sudo gem install xpreproj

   1	sudo gem install xpreproj

6. Install cocoapods

   sudo gem install cocoapods

   1	sudo gem install cocoapods

7. Run
   

   pod --version to test.

   1	pod --version to test.