I've been using Poser 4 Pro for a year now, but I have only noticed this problem recently. I can't say for sure, it could possibly be due to the fact that I'm using higher resolution bit- and bumpmaps than I've usually done before. But occasionally I've used hires textures and bumps before and not had this problem.

Does anyone know of there's a way around this problem, other than turning off bumpmaps? What's causing it?

I've seen dark areas when the strength of the bump map is trund too high. Reducing the strength got rid of the artifact. Don't know if that's what you're experiencing.

Yeah, I've had that too, but that's not the case here. For this particular piece (LM Stormguards outfit bought at DAZ) there's MAT presets, and like you can see the right side appears normal. Also it often, but not always, seems to be appearing on only one side. It's the same texture & bumpmap, so it must be Poser's renderer that treats on half of the texture/bump differently.

Strange. Also, with the bump on, eveything else with a similar texture (similar to the kneepads) has gone completely black. Have you looked at the .bum file or tried substituting a simple greyscale for the .bum to see what happens?