Garry's Mod won't start up

I got Garry’s Mod a few days ago and I got the new update that came out on the sixth I believe.

Long story short: I got update, and now I can’t even play it. It goes to the loading screen, cuts to black and sends me back to the desktop.

Can anyone help me with my problem?

(User was banned for this post ("wrong section" - postal))

Reference threads; people have been having this problem a lot for the past week.

[editline]8th July 2013[/editline]

Where is your Garry’s Mod folder located? /steamapps/(username) or /steamapps/common?


Thanks for the reference threads by the way.