Blarg! All computer products and software are useless. It's just that some are less useless than others.

All I can say is that I checked it on: Kobo reader, Adobe ADE, Calibre, Sigil, and the Firefox epubreader add-on. Had I a Nook I'd have tried that too.

I did a search on your "Opening your ebook" freeze problem and saw complaints that it happens but no real solutions.

The O'Reilly publishing people complained that their Nook wouldn't read many of their books and a commenter pointed out (as of early July) that the update to the latest firmware solved that problem.

The Barnes and Noble forum pointed out a solution that only works if you loaded the file via their software.

I'll do a little more digging but I'm not sure what could be the issue. Sorry that it doesn't work for you.