I've recently converted Rhen Var Harbor but I've encountered yet another problem.
When I play GCW the AT-AT stomp effect releases black squares rather than dust as
it should. Any ideas?

Are you using the bf1 or bf2 sides?

BF2 and BF2 effect.

Hmmm... I have no idea what's wrong. When I was making then var mountain, the probe droid orbital strike had the same problem, there were black squares instead of smoke. Make sure you have all of the required mshes for the effect, if there are any, for example once I had a prop effect with missing geometry and it turned up as black squares until I added the msh.

You need to put the names of the textures and FX files in your world's REQ file.

Okay I'll try adding the textures (the effects are already added) into the REQ.

-EDIT-
That didn't work . Here's the maps REQ: