uh, yes, we ran into the same problem here. When you go in the source code of pvmpov, you have to find the source file (probably conf.h or maybe png_pov.h or another one similar) and include your LOCAL png.h file instead of the one from your pvmpov source. This is because the png library on your system is the one loaded by pvmpov.
Hope this helps, I had the exact file name somewhere, but I got rid of the email too soon it seems.
Also, I finally got pvmpov 3.5 working, after a good deal of help from it's main developper.
You can find the source and binairy files on this website :
Good luck to you