Left 4 Dead Stuttering

Forgive a long winded one, but curious if anyone has any ideas.

1. Been playing Left 4 Dead for a couple weeks, runs fast smooth, no crashes.

2. Last night installed GTA4 and the new Nvidia beta drivers that are supposed to make it run better.

3. This morning go to play Left 4 Dead get the occasional game stalling/stuttering/sound looping and eventually crash.

4. First thought goes to GTA4 malware (SecuROM, GFWLive, Rockstar Social) so I uninstall all the GTA4 bits including the cleaning SecuROM out of Application Data and Registy. L4D still broken.

5. Second thought goes to Video driver. Back out video driver to 180.48 (including Driver Cleaner Pro wipe of "bad" drivers). L4D still broken.

6. Find the "mat_queue_mode 0" command, that fixes L4D problem.

Question: Any theories why L4D started croaking on me? Think GTA4 install had anything to do with it or just coincidence?

with the 180 drivers you cant use multicore, for some reason its bugged to make that one game stutter uncontrolably.

Use the Video -> Advanced -> Disable Multicore option or rollback to older drivers to fix the problem.

or, I just read this: you can run it in windowed mode and the stuttering might stop.

with the 180 drivers you cant use multicore

purple_MAN1832

Sweet info, that's probably it. I bet I had < 180 drivers to start with, upgrade caused the problem and I didn't downgrade far enough.