Problem with Source mods

Okay,

Everytime I try to load a source mod (that works with Source SDK 2007) I get this error:

"CFileSystem::Init() failed: failed to find steam interface"

I dont know how to correct this error and I am finally coming here to ask for anyone who knows how to fix this! My guess it has something to do with source sdk base 2007 (but i dont know).

Help would be appreciated!

Thanks,

Namby

Could be your antivirus blocking it.

How would I be able to turn off avast?

Not familiar with avast but most antifirus softwares allow to set up whitelists so you don't have to turn it off.

Google is your best friend there.

So I tried turning off the antivirus and it still gives me the error. Any other tips?

If anyone else could help me with this, that would be great