A simple name change of app-text/calibre-0.7.1.ebuild to app-text/calibre-0.7.2.ebuild does the trick. Strangely, the main window of Calibre shows that it's version 0.7.1, but the pop up doesn't pop up stating there's a more recent version to be had. More importantly, the 'find' bug is no longer present.
Thanks, this is in cvs now. I used sed to fix the 'version 0.7.1' issue that you reported.