FIX 1
This is for vista users (I'm unsure if it'll work for others). If at any point it comes up with the annoying 'are you sure?' messages, just click through them as per normal.
1)Navigate to your windows folder (usually c:/windows/)
2)Inside there, goto the CSC folder
3)Try to open the folder and it should fail (if it doesn't, you have a different problem). It'll come up with 'You don't currently have permission to access this folder' at which time you keep pressing continue until it says you've been denied.
4)Right-click the folder, go to properties.
5)Go to the security tab at which point it'll say 'To continue, you must be an administrative user with permission to view this object's security properties' at which point you click continue.
6)Click on admin in the owner tab which will swap the owner to the administrator then click OK.
7)You then click on OK once again which will bring up the security tab.
8)Tick 'full control', press OK twice to get out of the properties tabs.
9)Run the game.
fuloran1
FIX 2
Turn off multicore rendering
oct42
FIX 3
I use mat_queue_mode 0 in console and it fixes everything
The Red Ninja
FIX 4
If you have an NVidia graphics card and are still experiencing hitches please try installing their beta driver version 195.39.
Mike Durand
FIX 5
1. Close Steam
2. Go To ..\steam\steamapps
3. Delete left 4 dead 2 client.ncf
4. Delete left 4 dead 2 common.ncf
5. Restart Steam
6. Right-click L4D2 and Install
7. Let it sort itself out.
Freyar
FIX 6
1. RightClick on L4D2 and click on properties
2. Click on “Set Launch Options…”
3. Type the following “-lv” and hit ok
4. Play the game but be jarateed that you don’t have your gore anymore but hay it works.
DigitalySane
FIX 7
Disable VSync. This is known to fix some CTD and stability issues.
Soickan
FIX 8
Delete the clientregistry.blob file in your steamapps folder.
Then verify game integrity and file cache upon restarting steam.
Apoptygma Bzerk
FIX 9
Fixed it. Anyone else who is having this problem, set your graphic settings to either low or medium.
Tovrashi
FIX 10
1. minimize the game via ctrl+alt+del
2. go to processes, right click on left4dead.exe
3. click set affinity and uncheck all but one box so the game runs on only 1 core
<forum board>
FIX 11
1. In steam, right click Left 4 Dead 2 and click “delete local content.” Confirm.
2. Re-install the game
MeowMix