Apple TV 3 5.2 update stops playing movies

G'day

I've got a 27" late 2010 i7 16GB iMac running X.8.2, and an Apple TV 3. Just updated to 5.2 on the ATV. Latest iTunes on the iMac.

Everything is hooked up OK, and I've got 4 (out of 5) bars signal strength on the ATV. (about 10 metres apart)

The ATV plays everything through the router OK, including YouTube clips.

It also plays music OK (or seems to) from iTunes on the iMac, without failure.

However, all movies stored in iTunes lose the link when playing, and I get the 'Your ATV is not connected to iTunes, please connect' message after 1 to 6 minutes. I usually can regain the link with little delay, but it's a pain having to reselect all the menu choices.

I did NOT have any problems with 5.1

I've reset the ATV, and reset my iTunes Home Sharing.

Any thoughts on what's wrong please?