Actually I'm reasonably sure the error is not from the conversion program...
I've used it before successfully, but not recently. So today I am trying to convert some ereader books that I purchased in April and never got around to converting, and I'm getting the following error message:

Error: Incorrect eReader Version 10 (error 1).
:help:
Does anyone have any ideas on this?

The ebook is DRM-free. If you want to format shift it, try using Calibre 0.6.0 beta (http://www.mobileread.com/forums/showthread.php?t=48459).

THANK YOU, Wallcraft!