I couldn't find this fix as a guide on Steam and it doesn't seem to be well-known. It worked for me, although I don't know why.

1. Right click on the game in Steam
2. Go to "manage"
3. Go to "browse local files"
4. Delete iw5sp.exe
5. Right click on the game in Steam
6. Go to "properties"
7. Go to "local files"
8. Click "verify integrity of game files". This will take a minute or two, depending on your internet speed
9. Launch the game
10. Kill the bad foreign people