I've never seen this error before and nothing seems to be fixing it. Immediately upon loading any map I make I get this:
Fatal error: mod_numforname c:/program files (x86)/steam/steamapps/common/half-life/valve/m not found
If I make a map that uses a sprite, a sound, a gib model, etc, I get this error. I have a map that is a single room with one breakable brush that uses a gib model that results in this error. It does not matter what gib model I use, and they are not custom models or sounds, sprites, etc. Verifying integrity of game files has not helped.