WireShark latest build has some issues with Mountain Lion. This is how to install and make it work.
- Install X11 from http://goo.gl/jxABy
- Install Wireshark from http://goo.gl/CV637 (I installed OSX 10.6 version)
- Next log off and login in back
- Now open terminal
- Type: open /Applications/Wireshark.app/
And it should work. Above is a video for referral.