Windows user having the same issue. Been going on since iOS 5 came out. Every update to iOS/iTunes excites me, then disappoints me.
iPad 2
iPhone 4
iPhone 4S
iPad (3)
All had/have this issue. Reinstalling iTunes/Bonjour did not work, reinstalling windows did not work.
Using a Cisco linksys E3000 router.
I put a post on one of the apple discussions threads.