When I load a scene I have saved I get a message that poser(6) can't load a texture because it either can't find it or its too big. It appears that all the textures are loadedbut the scene won't render. It just stops. No error message or anything. The image was working and I'm not sure what had happened. Does anyone have any suggestions how to tell which texture it is? 

Not really, unless something is showing up in the preview as white.  It's happened to me a few times.  It generally happens if you're rendering a complex scene (like I do), or ridiculously big (like I do) or have a lot of reflections (like I do), and Poser runs out of memory.

I suggest you break your scene into bits, render piecemeal and put it all back together in Photoshop.  

You should also shut down Poser and restart it before trying to render again.

poser loads the textures in the order they appear in the pz3/cr2 file, as viewed in a non-formatting text editor. ya just go down the list and find the one with the bad/long/asyntactic path, or the one that's bigger than 40962 or whatever the limit for P6 was.