Can't convert mobi - is it encrypted?

[dixonge]

I have been trying to convert several .mobi files to epub format so that I can more easily read them on my ipod touch. Some of them can be read in XP using mobipocketreader. Even those get errors when trying to convert in Calibre. Others show up in the mobipocketreader library, but cause the app to completely crash when I attempt to open them. Others don't even show up in mobipocketreader at all!

All ebooks are sitting in the same folder in XP.

The ones that I *can* see in mobipocketreader all say they are not encrypted when I check file properties.

So are these files all corrupt or what?