The workshop used to work fine; I played a lot of custom levels. But now it's just stopped. I tried reinstalling the game a few times, wiping local content etc, but every time I select it again in the main menu it just freezes, and I have to close the game with task manager.

Every other part of the game works 100% fine, it's just the workshop, which unfortunately is the part providing all the replay value.

Any ideas?