Cache Needs Repair error

This error occurs when certain game cache files have encountered an internal problem (usually after a crash while running a game).

To repair the cache file:

1. Shutdown Steam by choosing Exit from the Steam task bar icon menu.
2. Restart Steam.
3. Run Half-Life 2 from the Steam Play Games window.
4. If the problem is not resolved, repeat these steps running Counter-Strike: Source and Half-Life 2: Deathmatch.

Running these applications causes them to validate and repair any cache problems they may have.