Check in Miscellaneous to see if the remove first image is checked.
There are a few more options in this section.
Remove first image
Sometimes, the source document you are converting includes the cover as part of the book, instead of as a separate cover. If you also specify a cover in calibre, then the converted book will have two covers. This option will simply remove the first image from the source document, thereby ensuring that the converted book has only one cover, the one specified in calibre.
Last edited by Gunnerp245; 12-12-2012 at 08:49 AM.
Reason: Added info