Windows 7 ultimate has stopped seeing 3 XP machines & two HP servers but sees Win 7 pro machine & still connects to the internet. Backups to server are still working. All the latest updates on all machines. Virtual XP on Ultimate machine sees all other machines. The only machine that still sees the ultimate machine is the Win 7 pro. The win 7 pro machine sees all the others. Up until 5 or 6 days ago all machines saw each other. Anybody got any ideas?