I've been getting some weird game performance over the last couple of days. At first I thought that it was from adding a second display, but I was still getting the FPS loss after the display was disconnected and gone. Then I updated my video drivers from 10.4 to 10.6, no change. Then I thought it was just Source engine games, but I'm having problems with Killing Floor and UT3 also (both using Unreal engine). I've made sure BOINC was off, and the card is running in the mid 50's. Edit: The problem is now confirmed to only be with games using the Source and Unreal engines. Good (normal FPS) Dirt 2 // 45-60 Lead & Gold // 60-95 Just Cause 2 // 45-65 GTA IV // 20-60 Trials 2 // 180-200 Beat Hazard // 60 Bad (below normal, all values are with vsync off) - Before, I could run these games maxed with vsync on and have them locked at 60FPS. Source - Unreal TF2 // 30-45 on high, 45-100 on lowest L4D // same as TF2 L4D2 // 35-50 on high (same with 3x buffered vsync), 60 on medium Portal // same as TF2 CS:S Stress Test // 82.58 (used to get around 160) Killing Floor // 7-20 on highest, 90-130 on lowest Unreal Tournament 3 // 35-60 on high and low Moonbase Alpha // 25-60 with all of the effects on Followed Erocker's video driver re-installation guide and the problem is now gone. Thanks everyone!