Singleplayer Error

So I go to start up a world I just got (I installed it, then restarted Gmod), and it gets stuck on “Starting local game server”. I had to restart my computer! This only effects one map (I think), which is “rp_stardestroyer_b4”. Please help!

This is already known. Read down from here in the official thread and see if you can find a solution that suits you.