Buffer/Meshes errors

when i was playing miltial i locked up and then a error saying

Engine error.
could not lock buffer/meshes

i took out tons of mods and still having problems, can someone help me thanks

[editline]08:56PM[/editline]

i just did a feash reinstall of garrys mod and i still get the error is it css thats causing it to crash should i reinstall that?

i did a reinstall of css and garrysmod
and still get the error
could it be garrysmod engine hope someone can tell me.