I haven't used P3do in a long time, but heard that it often causes a similar occurances..  I did manage to find a work around.. Odd and maybe a little tedious.. but it worked.

I ended up downloading and re-installing P3do in the end, and opened each the thumbs and resaved as rsr, then opened Poser and navigated to the folder with the problematic thumb, and voila it was there.. when I went back to the folder in Windows Explorer, it had created fresh png files.

~Wolfie~

Helping everyone is the most rewarding failure you'll ever experience.
    - Ray Augé (~Wolfie~'s hubby)

Anything is more stable than Windows . . .
--- Even a relationship based purely on sex!
    - Pam Augé (~Wolfie~)

No meat was harmed during the making of this TV dinner.
    - Pam Augé (~Wolfie~)