Recently I updated GhostScript and NetPbm on my Windows box, and found the latex2html started to report errors when generating images. The error messages said "bad file descriptor" when executed pstoimg.bat. Google gave several pages that contains exactly the same symptom of this problem but no solutions. Some suggested to use the debug mode of latex2html to see more detailed tracks. It really helps! I found the NetPbm executable file was trying to locate a file named rgb.txt, and it tried several places that are the directories on Linux systems, but failed. It also suggested a RGBDEF environment variable. The file is in the misc directory of the NetPbm I installed. After I set the environment variable, the problem is fixed.
It seems that all applications better have a DEBUG mode.