Garry's Mod Crashing

So recently I was trying to get on single player to start a Hamachi server with my friend and I. I get to “initializing game data” and when it looks like it’s finished, Garry’s Mod crashes. I haven’t downloaded any mods and I just don’t understand why it’s crashing. If anybody is wondering, joining a friend’s or multiplayer server works.

Try verifying the game’s cache by doing as follows:

  1. Go to your Steam Library where Garry’s Mod is.
  2. Right click on Garry’s Mod and select “Properties”.
  3. Go to the “Local Files” tab and press “Verify Integrity of Game Cache”.

Let it run, and if anything is missing/broken it should automatically be downloaded and updated.

Still not working. I don’t understand what has caused this.

Oh, I’ve fixed it. It was an addon causing the problem.

For future reference, there is a help section on the forum, http://facepunch.com/forumdisplay.php?f=16