I just started getting this error today! Prior to today, I have been able to sync via USB or WIFI without issue. Today however, my phone would not sync at all via either method. I tried rebooting the phone and that fixed the problem, but I suspect it may rear it's ugly head again.
Hmm. A reboot didn't fix it for me. Although my sync does work when plugged in, as before I realized I only had the end plugged into my phone and not computer... whoops.