Gmod - Cannot play single player, or create multiplayer

[Geat]

Hey guys, I cannot play single player, or create multiplayer ( I click the button, and get nothing)...I can only join other servers, and about 9/10 times, it fails...The server will be fine, and the window for the server (With refresh, join game etc) will just flash up each time I press connect...Even worse I can't see whats wrong with it because the console wont show, and it IS binded/enabled.

Other things that I cant get into is the gmod settings, and the ESC menu in-game.

I really don't want to have to reinstall this.

So before I do, has anyone heard anything like this, and had success?...also I have tried restarting, it made the problem significantly worse.

Although they're probably not relevant, here are my Specs:

Graphics Card:
Name:NVIDIA GeForce 7600 GS
Total memory: 512MB
Disp.mode: 1280 x 768 (32 bit) (60Hz)

RAM: 2 Gig

[Whiterfire]

I think someone hacked my account! It says someone is logged in a different location.

Go to C:\Program Files\Steam\ and delete the file called "ClientRegistry.blob".

[Geat]

Alright, I'll try that. Thanks.