Welcome to MobileRead.
Originally Posted by Deering91
I have an epub version of a free (no DRM) book that I am trying to convert to MOBI to put onto my Kindle Fire HD.
I don't have an answer to your question, but the sticky post
discussing info required when asking for help with conversions states you should provide the conversion log. All of the conversion log not just the part you think is applicable.
Hopefully someone with some insight will be by to help.