In general terms, under most conditions, you cannot simultaneously synchronize the same data type to more than one environment - to iCal and the Address Book using iSync, and to the Palm Desktop - while logged on using the same user account. If you and your wife are sharing the same user account, then the place to start is to create a separate account for her. It can be an administrator level account - it just cannot be the
i same
account as yours.
As aside: sharing is difficult, particularly in a high-technology environment. It's better, in many ways, to lead 'separate' technological lives.
Depending upon how the Palm Desktop and its components, and the Address Book, iCal and iSync are installed, you may have to install additional copies in her new adminstrative account. Once you've done that, you can configure each account to synchronize separately. And these will be distinctly separate accounts that do not share data. To overcome that intially, you can export vCard data from your Address Book to import into her account, and you can each publish calendars to share if need be. There a lots of options here, so be sure to read up first in the iCal and Address Book Help files about sharing data. You may choose to share data in some manner, but you will synchronize separately.
