it happens on all of the games i've tried (except for CSS, HL2,etc.) the following games have screwed up so far:
Warhammer 40,00 Dawn of War
GarrysMod
Lemming Ball Z (freeware)
Quake 3 (and team arena)
Before you say these might ont be compatible, Q3 and TA worked before. Now that i think opf it, it started when i installed GarrysMod. I'll see what happens if i uninstall it...