"Steam has found a problem with your local game file"

Hey guys,
i came on today and it came up with this error:
http://img12.imageshack.us/img12/8931/bobmarleyg.th.png
so i reinstalled it restarted my pc, defraged it and all
it stll doesnt work please help

[editline]07:45AM[/editline]

it says:
“Steam has found a problem with your local game file.
Game files will now be re-acquied from the steam servers”

[editline]09:08AM[/editline]

Help!

[editline]09:37AM[/editline]

BUmp

Please i wanna play

Try right-clicking on GMod in the Steam menu and choosing “Delete local content”. Then reinstall it.

I have done that