Problems with Garrys Mod :: Zombie Survivor

[Paul_Canning]

So I bought GM the other day, and wanted to play some Zombie Survivor.

However, I keep seeing the horrid purple and black checkered pattern and big red ERROR blocks in the maps.

I have HL2, Ep 1 & 2, Portal, TF2 and CS:S all installed (i bought the Orange Box, CS:S isnt mine, its my mates, so it says pre-loaded for me)

I am thinking the problem is because my account doesnt have access to CS:S but GM should at least be able to use the resources surely?

If this isnt the case, anyone know what might be wrong?

Thanks in advance!