Comment 4 for bug 1239176

I didn't have any problems with the conversion freezing calibre. Both books were converted within seconds. It's just Sigil that freezes for quite some time when opening Witz und Weisheit der Scheibenwelt.

I've opened and saved both ePubs in Sigil now. It did show a message that the ePub is invalid and repaired them. The repaired and converted files can now indeed be opened on the Kobo. The interesting thing, though, is, that Sigil 0.7.2 had no problems opening both ePubs and did not complain about any HTML errors even when checking with FlightCrew. Even in the new version 0.7.3 the only HTML errors are about "nbsp" entities, which, according to this thread (http://www.mobileread.com/forums/showthread.php?t=219360#9) is apparently a bug.

So I'm not really any wiser than before, other than the total restructuring Sigil performs on ePubs "magically" fixes the problem.