Solution to the mss32.dll
I had that problem and found a solution.
First, just to make sure if it haven't been done, do a integrity check of the game. Only about 15% of the case are repaired with that, but if you're in that small pack, this would be the fix.
If that didn't fixed anything, go to your game folder :
or (for Valve related games like TF2, HL, GMod, etc.)
In the game folder, you should see a "bin" folder. Either delete it or move it to another place. (far away from the game's folder). Do another integrity check and launch the game.
The bin folder will be recreated like new and the launching error will be gone.