Garry's Mod 10 crashing when I load games on custom maps

[NotTheOne]

Garry's Mod 10 seems to be working fine any time I start a new game or load a game on a standard pack map, but any time I load a game on one of my own custom maps, Gmod invariably crashes 3-4 minutes in. I thought I heard at one point that saved/loaded games were malfunctioning (when in the history of GMod have they not done so?), but I could be mistaken.

It also seems only to malfunction like this on my custom maps, at least, maps like aim_doubleroom that I've downloaded from the Garry's Mod download DB seem to function fine. Could there be an entity or command I'm leaving out of my maps?

Does anyone know what would make loaded games crash on my custom maps? Is this a known problem? Is there a known solution?