Hello, I 3lso have the same issue.
I elected 2 weeks ago to upgrade itunes and iphone 4 software which seemed to only upgrade itunes as it crashed during install. Now my PC running XP SP3 won't see iphone at all claiming USB malfunction at device. Itunes won't see it either which means i can't upgrade the iphone software either. No way it seems to roll back the phone without using itunes.I found a windows hotfix that addressed this specific problem "Fix CCS MaxSubkeyName mismatch File version 5.1.2600.5614", applied it but no joy.Had to know where to go next?/