I was having problems converting a chm to epub and my reader kept restarting when I got past the ToC that Calibre generated.
After much editing, I found out there were stray "<td>"'s (not part of any "<table>") after removing the strays from between ending and opening table's I was able to read it on my reader.
My problem is the same as old Ticket #6166 (epub converted from chm crash sony reader)