Cannot load any custom maps

[mydearwatson]

All the default gmod maps work fine, but every time I try to load a custom map I get this error:
[quote]
CModelLoader::Map_IsValid: 'maps/freespace_revolution.bsp' is not a valid BSP file
map load failed: freespace_revolution not found or invalid
[/quote]I've tried reinstalling, defragging, verifying, and just about anything else I could think of but nothing helps.

[a7y]

Where did you get Garry's Mod?

[mydearwatson]

Through steam years ago... this is a new problem

[a7y]

Try this: [url]http://wiki.garrysmod.com/?title=Cleaning_GMod[/url]

[mydearwatson]

Nope... Still nothing