Me too. I have the same problem since April, and I have a video to show the exact steps how to consistently reproduce this "FaceTime Sleep Bug".
Hopefully together we can get Apple's attention to fix this problem for all iPad 2 and iPod Touch users.
It finally seems to work (2nd day now and counting)...
I tried the following with no luck:
- upgrading to iOS 5
- adding an associated e-mail and calling that associated e-mail
- do a full-scale registration of the e-mail (and making a free purchase via itunes) instead of a 'facetime only' registration
this combo however seems to have done the trick:
- keeping the ipad2 plugged in
- changing the dns on the ipad to "126.96.36.199,188.8.131.52"
If it continues to work for a few more days, then i think i can say the the problem is finally resolved.
Have you tried to unplug the ipad yet to see if the problem comes back? The only thing I haven't tried to fix this problem is changing the dns numbers. If my ipad is plugged in, facetime will ring. If it's unplugged and asleep I keep missing calls. For me, I'd prefer not to keep it plugged in all the time.