Couldn't CRC map maps/cs_office.bsp, disconnecting

WTF! I just bought CS:S Yesterday and I can’t play cs_office in GMod!!!
Here’s the full error report in console…

No pure server whitelist. sv_pure = 0
Map [maps/cs_office.bsp] has incorrect BSP version (2405844 should be 20).
Couldn't CRC map maps/cs_office.bsp, disconnecting

Host_Error: Disconnected

Looks like it’s corrupted. Try verifying your cache (for Counter-Strike Source).

Did you mount the CS:S game content?
Did you launch CS:S at least once, and load a map once (A map, any map)?

How do I do that?

I launched the game atleast once yes. I played on lots of maps also!

In your My games list, right click on Counter-Strike SOurce, go to properties and verify integrity of cache.

hmm wow long time ago, BTW I fixed this by extracting the map from the GCF and putting it in the GMod maps folder.