Some iPad 2 users are seeing their FaceTime app freeze for no apparent reason. There's an Apple Discussions thread about the issue, which has already garnered 25 replies at the time of writing. User CRK The Man started it late last week with the following post (although there's two and more threads about the problem as well):

When I opened up FaceTime the first time, the camera was working fine, but now whenever I open it up, it just shows a still image from when I left. How can I fix it?

It appears that the iPad 2's front camera locks up in the FaceTime app when attempting to establish a video call (although some users found that the back camera can cause freezing as well). It's unclear how widespread the issue is, but it seems to be stemming from a software bug. This is better than a hardware issue since Apple will hopefully be able to address it in the next iOS release.

A couple of users say the same problem is happening with their iPhone 4s, so this could be an issue with iOS 4.3. The problem won't go away until the iOS device is restarted, although some went as far as resetting it to factory settings (via a full software restore).

FaceTime is only available on iOS devices with a forward-facing camera. To take advantage of the forward and rear cameras on the second-generation iPad, Apple added dedicated applications for taking pictures and shooting movies.