I am running the latest released (not beta) version of iTunes, 10.3.1, and calibre 0.8.5 under OSX without any problems.
I don't support beta software, it's challenging enough to keep things working with the released software in multiple OS's and configurations.
The error you're reporting indicates that the the iTunes automation is not working correctly. I have seen some tweets suggesting that following the directions in
this Apple support doc resolves some iTunes problems with iDevices. You can also try reinstalling iTunes, and of course restarting your system.
If none of those suggestions help, then I can only suggest that you revert to the released versions of iTunes and the iDevice firmware.
G