Firewall blocking fullscreen applications?

Running Windows 7 x64.

Whenever I would attempt to run an application in fullscreen, the monitor would blank out.

Something wrong with the Firewall security
whenever I try running 3DMark06, Left4Dead and Battlefield Heroes the monitor would go blank

If I set the Firewall Security Level to Disabled, I can run them all fine.

Am confident firewall pop-ups are not causing the problem, I can run Lead4Dead in window mode, no popups appear

I have tried adding Left4Dead to new trusted applications but monitor still goes blank

I don’t know what to do

Do you have Defense + enabled. Then you are most likely missing the D+ alerts. The best way to go is to put D+ in Clean PC mode or Training mode before starting those programs. D+ will now make rules without alerting. Run the programs for a couple of minutes and put back D+ to its previous state.