According to several threads on the Apple Discussions forum (here, here and here), the iPad’s front camera locks up in the FaceTime app when attempting to establish a video call. It’s unknown how widespread the issue is, but it seems to be stemming from a software bug likely to be addressed with the next iOS release. According to users posting on the forum, the problem won’t go away until device is restarted.
Other hiccups are also being reported. One poster details the issue:
Facetime was frozen on iPad 2. It had the last video capture as the main screen of Facetime. Could not see receiving video. Resolution: Reset to factoring settings. Apple – possible app glitch.
Another user is having troubles with the back camera, too:
I had this problem on my iPad 2 as well. I restored the iPad and it was fixed, but during a FaceTime call I switched to the back camera and it froze the video on both ends of the call (but NOT the local video / video of me on my end and video of them on their end).
Apple yesterday updated the $0.99 FaceTime for Mac app with improved performance when FaceTime is taken full screen.