Originally Posted by MontyJ
That was a GREAT idea! But, it actually made it worse; I tried one book convert and it crashed. A least my original config let me do one at a time, but not two or more.
I then ran the 32bit version and it converted that same book ok.
Some fonts have been known to cause problems. Go to Preferences - Look and Feel - Main interface tab and change the font to Ariel. Restart calibre see if things improve.