iphone wifi syncing issue with itunes 10.7

My wife and I each have iphone 4's syncing on our respective computers running Win XP Pro SP3. After upgrading to itunes 10.7 and iOS 6, itunes doesn't reliably sync via wifi. It will sync once then won't a second time unless the computer is rebooted. If I try and click the sync button on itunes, it looks for the displayed iphone then says it can't find it and the iphone disappears.This is happening on both computers. I can direct connect the iphone with usb cable and sync, but it won't sync via wifi without rebooting. I've click the "sync with wifi" button off then on. Nothing works.

We both upgraded to iphone 5's. It didn't solve the problem. I upgraded my computer to a new desktop running Win 8 Pro. Everything transferred fine and the initial sync went well, but the problem persists. After my iphone 5 sync'd with itunes overnight, the next morning it wouldn't sync again via wifi. Again, trying to initiate a sync from itunes caused the it to look for the iphone and not finding it, the iphone disappeared from itunes. Once I restarted Win 8 and itunes, the iphone showed up in itunes.

It's not the iphones(it happened with both 4's and 5's), the computers(two differnet computers) or, the OS( happens with Win XP and Win 8) so it's got to be an isssue with iTunes 10.7 and possibly it's interaction with iOS 6. We didn't have the problem before 10.7 and iOS 6 (upgraded same time).

Any suggestions? This is annoying to not have these reliably sync without intervention.

Thanks,

Z