You may need to completely reset sync data on all computers and on .Mac.
FIRST: RESET SYNC HISTORY ON EACH MACHINE
1) Move the 'SyncServices' folder to the Trash. This folder is located at:
where '~' denotes your home folder.
2) Restart your computer or log out of your account and then log back in.
3) Empty the Trash.
4) Launch SOHO Notes or SOHO Organizer. You'll be asked if you want to synchronize contacts, calendars and notes by the System. Your answer will depend on which type of data you want to synchronize. Quit the SOHO application you just launched.
5) Repeat these steps on each computer.
SECOND: UNREGISTER ALL COMPUTERS FROM .MAC THEN SYNC YOUR FIRST COMPUTER TO .MAC
1) Open the System Preferences (Apple menu > System Preferences).
2) Click the .Mac button and then click the Advanced tab.
3) Select each computer in the list and click the Unregister button.
4) Once all computers have been unregistered a 'Delete Sync Information' window will appear.
5) Select each item in the list and click Delete. This will delete all information on .Mac.
6) Click the Sync tab and select 'Synchronize with .Mac'.
7) Select one or more items to synchronize such as Contacts, Calendars, Notes, Bookmarks, etc.
8) Click the Sync Now button. A Sync Alert window will appear asking you what you would like to do for the first sync. Choose 'Replace data on .Mac', and click the Sync button.
9) Repeat steps seven and eight until all items have been synchronized with .Mac.
THIRD: SYNC YOUR OTHER COMPUTERS WITH .MAC
1) Move to your next computer
2) Open the .Mac System Preference Pane
3) Click the Sync tab
4) Select one or more items to synchronize such as Contacts, Calendars, Notes, Bookmarks, etc.
5) Click the Sync Now button. A Sync Alert window will appear asking you what you would like to do for the first sync. Choose 'Replace data on this computer', and click the Sync button.
6) Repeat steps four and five until all items have been synchronized with .Mac.
At this point, all your computers should be synchronized.