I have this problem too. I have tried the "solutions" suggested above. Sometimes it seems that the problem goes away, but it comes back within a day or two every time. I have four devices set to wi-fi synch and this error seems to happen with any of them. In the hope that Apple does monitor this forum, my configuration is:
Win 7 64 bit
iTunes 10.6.0.4
All 4 devices are updated to iOS 5.1
Devices: iPad2, IPhone4S, iPad1 and iPhone3S
Wireless network provided by two Airport Expresses. Win 7 machine running iTunes is wired.
Regarding the advice in this forum: all devices are set to back up to the cloud (not locally), 2 of the 4 have password lock set, I really need the synch for music as well as podcasts (a 400GB collection does not work for iCloud) so iCatcher is not a fix for me.
This is really a problem. I have had it for months and hoped that it would be fixed in the IOS5.1 / iTunes update, but it has not. The update has slightly changed the behavior: prior to the update I would get this post's error and frequently it came with a second error "An iPad has been detected, but it could not be identified properly. Please disconnect and reconnect the ipad, then try again." Since the update the second error does not seem to happen any more.
