In case no one else has suggestions, I'd try defaulting WinSock back to original status, (netsh winsock reset catalog from a command line) see here and maybe resetting TCP/IP stack (see here). [edit] Though TCP/IP probably isn't relevant here, see next line for why I needed that as well, does USB syncing involve the TCP/IP protocol?
As mentioned in the 2nd link, do check which LSPs are currently residing in your system, as an example, I had to re-install NetLimiter when I ran this command. (I had similair issues to you on a previous install of XP, but with WiFi syncing on a PPC)
With both procedures, please make sure you're confident of what you are doing, and more importantly, how to recover if things go wrong.
If you do try the above, hope it solves problems.