Hi J.E.,
Here's the scoop, which I tried and it worked, straight from the .Mac people:
To resolve this issue, you may need to remove all iSync data from the location that has erroneous data and replace it with known-good information from the location that has the correct data using iSync's Reset All Devices command.
Before deleting or resetting any data, you should back up any current data that you wish to keep. For more information about how to back up your important data, please see the following article:
How to back up and restore your important Mac OS X 10.4 files
<http://www.info.apple.com/kbnum/n301239>
First, remove any devices you have added to iSync by selecting them and choosing Remove Device from iSync's Devices menu. When you are done, iSync should only display two icons: .Mac and Sync Now. This will prevent data on your other devices from being altered.
The next step is the most important: determining which set of data you will regard as the master set, the set on your computer or the set on .Mac. Once you have decided on your master set of information, you can direct iSync to remove the data from all devices and replace it with the correct, current set.
Next, make sure that your master set of Address Book contacts, iCal calendars and To Do items, and Safari bookmarks are complete and correct. The information on all of your devices will be permanently removed and replaced with this data.
Once that has been done, proceed with the following steps:
1. Open iSync.
2. From the Devices pull-down menu select Reset All Devices.
3. From the Replace data on all devices with data from: pop-up menu, choose the location of the master set.
4. Click Reset All.
Once the reset is complete, you should be able to sync without further issue.
If you are concerned with losing all of your data, always be sure to back up first. You can back up iSync data by doing the following in iSync:
1. Click on Devices.
2. Choose "Back Up My Data".
