Facetime: Calls delayed by 10 minutes from call to receipt

I've noticed some very strange behaviour with FaceTime.

If I make a call from my Mac to my wife, on the Mac FaceTime starts, but does nothing. The call ultimately gets through to my wife, but after _10 minutes_! As in there is a 10 minute delay from when I press call, to when the call arrives on her phone.

The other oddity, is that if I try to enter the FaceTime settings on the phone, there is a very long delay - the phone seems to freeze before allowing me to enter. I tried starting, without so much joy.

Unfortunately, this combines to make FaceTime essentially unusable :-(.