In my ignorance of the details, I can't help but think that this should be a pretty easy fix on Apple's part, by simply configuring the tethered sync to include whatever configuration necessary to ensure an error-free wireless sync. (at least add the wi-fi sync to the diagnostics in iTunes)
It seems there are a number of us running into this problem, and there doesn't seem to be a cure that doesn't involve a hard reset to factory settings (and I don't even know if that would fix it). I have over 100Gig just in music in my library. Uninstalling and reinstallin iTunes isn't a quick 15 minute process like it used to be.
iPhone 4, iOS 5.1.1, Wi-Fi sync - iTunes/iPhone not talk