My P1i hangs often during the phone reboot process during backup or recovery. It does not happen every time, but often enough to be VERY annoying. It's wasn't a big problem my recent attempt to migrate the sync to my new notebook.
My P1i would go through the backup process and everything would be fine until the reboot. You can see the boot start screen on the P1i with the startup status bar moving to about 80% of the screen, then stops. Then the phone would hang until the Backup Manager on the PC gives an error saying that it lost communication with the phone. The only to turn off the phone was to remove the battery.