The memory could not be "read" error

About %90 of the errors i get in Gmod are something along the lines of this:

(Big image alert)

Anybody know much about it?

Edit: I just got it again, trying to join a different server…

Edit: NVM it was my custom addon, which contains CS:S models, anybody know why it might be crashing me?

I don’t know why it would crash, but I would recommend removing it and just buying CS:S.

Eh, no i forgot to say i own CS:S but i was testing an addon for my friends that i made so they don’t have to have errors in RP anymore, just missing textures.