This patch was needed for tex4ht to work properly with a file I was trying to convert:
https://sourceforge.net/p/pgf/bugs/327/
It looks like it has still not been merged upstream, but you may want to merge it to the MikTeX pgf package in the meantime.
Also, you may want to use the latest tex4ht upstream, which includes a patch for this issue:
http://tex.stackexchange.com/questions/161229/htlatex-interrupted-at-temprm
The upstream at http://svn.gnu.org.ua/viewvc/tex4ht/trunk/ already has the patch, so I think you should only need to include the new files generated by running "tex tex4ht-4ht.tex".
MiKTeX includes the latest CTAN available pgf package.