Facetime
I have Facetime on my iMac.
When I try to connect to someone I immediately get 'end'.
When I click on 'end' the application reverts to the list of contacts.
On my iPad Face time works fine.
I notice on the iPad the contacts with video have a mini cam besside their name.
On the iPad they have a star.
The Facetime is ON in the preferences.
iMac, OS X Mountain Lion (10.8.4), 2.4 mhz, 21"