SOLUTION FOUND!!

After much hair-pulling, i found the problem. Thought i'd share it with the Poser family since there are still some Poser 4 users (in the closet)

turns out Poser 4/ProPack didn't like the 3GB RAM on my system that i had just installed. It didn't dawn on me that you could have too much RAM! Since Poser 4 has memory issues i guess that's one of them back in the days when 3GB Ram was unheard of.

Anyway, i scaled back to the original 1GB of RAM and Poser 4/ProPack worked fine. Then i added one more GB and it seems OK with a max of 2GB.

That explains why Poser 4/ProPack didn't work on my brand new Windows XP machine, with 3GB Ram, which really threw me for a loop.

Hope this helps someone else if they run into THE NIGHTMARE ON Poser 4/ProPack STREET!

thanks to all who responded!