It seems it's P3 figures that cause the problem. With some, Poser 7 just crashes completely; with others it just comes up with a blank window, but seems to know that the figure is there.

I would certainly have expected it to be backwards compatible with a basic figure. Something in the pz3 must be incompatible. If I could find out what it is I could probably edit it, but how on earth do you go about finding out where the problem is?