I just ran into the same problem. It looks like it's caused by attributes on tags with values that are not in quotes. For example, if you're converting rtf or doc to HTML using Word, classes are generally not quoted (class=MsoNormal rather than class="MsoNormal"). Apparently some change in HTML processing 0.7.5 no longer likes that. In my case, I was able to clean up the HTML easily enough, adding quotes around unquoted attributes.
Hopefully it's just a bug and not a new feature