Having problems getting game to launch, gets to the opening video then kicks me out

[Airmail]

Says I get an engine error which then reads "Invalid file id for c:\program files\steam\steamapps\common\left 4 dead 2\left4dead2\resource\closecaption_english.dat

One night my game worked fine, the next day I get this, I haven't done anything weird with the game other than play it like I have for years, if anyone can give me a hand figuring this one out I'd appreciate it, thanks in advance. =)

[THEBIGREDMACHINE]

First thing I would try would be to verify the integrity of the game cache.

Go to your library and right click on Left 4 Dead 2. Then click on properties. Then click on local files. Then click on verify integrity of game cache and let it run until it's finished.