'Not Compatible with this signal' Problem

[Toasters]

I just have a question: anytime I try to open up Team Fortress 2 on my computer, The screen will go black and a box will pop up and say, 'Not Compatible with This Signal'. The game is running in the background, as all the sound is still playing. I am using Wifi, so could that be the problem? I don't know. Could someone help me? Your help would be greatly appreciated.

 

[FireHazard772]

Haven't heard of this problem so did a search. Couple of steam-forum threads that might help:

http://forums.steampowered.com/forums/showthread.php?t=2521088

http://forums.steampowered.com/forums/showthread.php?t=1266924