Stuck at "Preparing to launch Garry's Mod..."

Yeah, title says it all. I can’t start GM since it does not go any futher then that loading screen. GM has worked perfectly, no problems till today when suddenly I can’t start it.

Solutions please?

Verify the integrity?

I did that.

Try renaming your garrysmod folder (in steam/steamapps/<steamname>/garrysmod) to garrysmodold or something and then start up Garry’s Mod.