I am
installing Snow Leopard
but it was more or less what happened to me before.
Workaround I found in the forum: Uninstall the ebook library, then Pref panel, International, change both language and format to US English + US or any combination with the "supported" languages (English, French, German, Dutch). Reboot, reinstall (reboot...) and then it should work. You can go back to the original prefs on language for sure, but I have not tested the change for the format panel.
Hope I was (barebone) clear
(re: Callibre. I love it dearly, but let's face it: we're still a long way from having ieBooks. ITunes, at least on Mac, it nice, simple and directly connected to the Store. We still have- and this is true also for PC users!- to juggle between multiple programs. Who knows, if they do the Mac Tablet
maybe they could get on working on eBooks management. We're waiting...)