Well folks, something that didn't strike me until now was to try my pants out in DAZ Studio. In spite of my glorifying words about the app I rarely use it nowadays in favor of Carrara. And everything works just fine with the textures in Studio. So, all is well with my pants in both Poser and DAZ Studio but not in Carrara. We got a Carrara problem then, eh?

To sum it up, the mesh behaves in Carrara as if it wasn't UV mapped. That is, I can change colors in the shaders but not use any textures.

This must be a bug in the Poser content import process. Or simply some kind of memory issue in Carrara. My figure works in both Poser and DAZ Studio but then again, Carrara is not primarily built to handle Poser content. It would just be interesting to send my figure to DAZ and see if they could figure out what's wrong. But I'm afraid they don't have that kind of support.