I have access to some tools like Mobi_Unpack.py and DumpMobiHeader.py that should be able to let us compare to see what has changed.
Please find an older calibre mobi conversion from an epub in your library that works and save it and then convert that epub again using the latest calibre and verify that the new conversion is faulty.
Then post a zip archive of both the broken and working mobis. And it wouldn't hurt to include the original epub as well.
With the Mobi_Unpack.py and DumpMobiHeader.py tools, we should be able to see what if anything changed to help Kovid track down the issue.
Originally Posted by Cinderela
Since the OP hasn't responded and I have been having the exact same issue with my KF, I performed this test. (I am using the current 8.47 version of Calibre. This problem started around the time Amazon pushed the most recent update and Calibre upgraded to version .47)
The Smashwords file sideloaded worked fine. So, I guess this is a Calibre conversion issue.
The symptoms of my problem are even weirder. The epub-to-mobi files are read with no problem on my Kindle KB, but perform the "open then close" routine on my Fire. (But not *every* converted file, just some - and I haven't been able to find anything in common among the files that won't open.) I've tried resetting/reinstalling/reformatting/reconverting with every option I could search for on this forum, the Amazon Kindle forum and the Calibre help section.
At my wits end!!!!
I love my Kindles (Amazon WILL synch last page read on sideloaded files) and Calibre, but I've run out of things to try!
This probably should be moved to the Calibre forum - Mods, can you take care of that?