Mobi error from one library, not another

[Dorney]

Hello. I've recently purchased my kindle, and with Igorsky's wonderful tools have been able to download ebooks from a library. I have access to another library, and tried to download their ebooks. The problem is a Mobi error I'm getting: "The retailer website from which you have downloaded the eBook --- could not be identified, please redownload the eBook directly from the retailer website". The file comes to my directory, and can be kindlefixed and transferred, but I can't open the book on my kindle.

Has anyone else had a similar problem, or have any ideas what I'm doing wrong?

THANKS!