Source SDK Error (Can't Start Up)

[navyseal2004]

I've got an error which says : MountFileSystem( 221 ) failed : SteamMountFileSystem(2988,221,0x663fbfc=,0x663fd0c ) failed with error 116 : Cache needs repair

What does this mean? What do I have to do?

 

[Faulk_Wulf]

Run Half-Life. It will validate some files. Then SDK will be fine. Or if you're mapping for CS:S / DM, run them. If you're unsure, just run them all until something gets validated. This usually happens if Hammer, Half-Life 2, or your computer crashes while working on a map. Hope that helps.