I have a Windows 7 x64 Enterprise system. I've installed Windows XP Mode, Windows Virtual PC, and the update. Everything was running fine for a time, nice integration and all that. I don't run the XP Mode VM all the time and eventually I launched it and it failed to log in to my domain. The nasty part is if I switch the network settings from "NAT" to my physical adapter it can contact my domain and log in. However, if I hibernate and launch again I have to switch the network settings back to be able to log in again.
So no matter what the network setting is on, NAT or Physical, on each launch I must switch it to the other one for it to be able to contact my domain and log in.
I do have VMWare Player and VirtualBox installed on this machine, but neither is running when I attempt to do this. I've installed all available updates and not sure what else to try. I recently uninstalled the Windows Virtual PC update, rebooted, reinstalled, rebooted and it has had no affect.