Have you tried uninstalling and then reinstalling the game? Might not work, but it's worth a shot.
You say your drivers are all up-to-date. Are you checking the manufacturer websites, or are you relying on a 3rd-party solution for driver updates? If you haven't, then I would advise checking the manufacturer websites for drivers.
Next up...You're using a router to connect your 3 home machines to, correct? If so, try changing the port on the router of one of the culprit machines with the working machine.
If all else fails, you could backup the data on the culprit machines, and then format the hard drives.
Best of luck!
-Eloricth
PS: Game runs fine on my nVidia card (8800GTS 640)
