Garry's Mod crashes itself and steam when accessing certain maps.

This has happened for two maps so far: Rp_city45_2013 and Rp_Littletown.

Whenever I try to access a sever with either of these maps, or if I’m downloading it from Workshop by going onto the main menu, it crashes Gmod and steam.

I’ve done clean installs, I’ve removed addons (how I found out it was the maps) and verified files. I can play other maps, and I recall playing on Rp_city45 some time ago without this problem, but it seems to have spread to it.