Originally Posted by user_none
At this point you might have to because I can't reproduce it.
Could you try again, but convert to rtf, not txt? I can't reproduce the problem in txt, but can in rtf when converting from a test zip file and from the original epub. The test zip is just a basic html file added to Calibre having a single paragraph <p> with <html>, <title> and <body> tags. Make sure the breaks in the para are just 0x0A.
Debug during conversion shows no problem at any of the 4 intermediate output stages, so I assume it would be in the rtf output stage.
No. I spent last night doing an image restore of my entire computer to last week's status and this morning putting back some settings that had changed. The computer's stable again. (Something bad happened when upgrading AVG antivirus - it's now gone.)