I've had this a lot. Using the python scene inventory script I found out that poser wasn't looking where it should for the texture files. It was inserting another file level that simply didn't exist on my system.

eg: E:RuntimesV4-A4 ClothesRuntimeTexturesBillyTLeatherW_Leather_Jac_Spec.jpg
       E:RuntimesV4-A4ClothesRuntimeTexturesBillyTLeatherW_Leather_Jac_Spec.jpg

The first line is where it should have been looking, the second is where it was actually looking. I think it had to do with the space, although P7 worked fine like that for six months before it started with this. I tried everything to fix it, deleted preference files and whatnot and nothing short of a full uninstall/reinstall (including all the stuff it hides in my docs) fixed it.

The second time it happened my very clever boyfriend set up some sort of virtual shortcut to save me the stress.

Don't know if any of this helps at all, but if none of the above works, load up a scene that's giving you hassle, run the script and have a look :)