You should be able to use more than one image per object...you can have one per material (usemtl) actually. Normals and UVMapper Regions shouldn't cause any problems either because Poser doesn't even read those (at the same time, Poser doesn't read those so I generally delete them from my object to cut down on file size).

I thought maybe something else was in play, but it doesn't sound like it now. I'm now thinking that maybe your obj plug-in is corrupt. You may wish to manually delete it and reinstall Poser (after backing up custom items first to be on the safe side).