I've seen this before, this always happens to me when I do not save the PW zip file to my harddisk first. When I do download without saving the file and try to open it then it's empty. When you click on a PW file, never use open, but always use save (the second button, not sure what that states in english) and open once saved.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk