Well,
They responded to me query and the solution is just a simple 15 STEP procedure. Nothing at all, shouldn't take up too much of your valuble time.
"Thank you for contacting Apple.
To isolate the Safari Bookmark that is causing a sync failure, use the split-half approach. You should repeat the split-half approach until you have identified the bookmark preventing a successful sync.
To perform the split-half approach on your bookmarks, please follow the instructions below. We recommend reading the instructions fully before attempting the prescribed actions.
1. If Safari is open, quit Safari. Make a copy of the ~/Library/Safari folder (when "~" represents your Home folder). To do so, control-click the folder icon and choose Duplicate. This will create a folder called "Safari copy." This creates a backup copy of your Bookmarks that you will use as a replacement after troubleshooting.
2. Open the Safari folder and drag the Bookmarks.plist file to the desktop. Open Safari and then sync using .Mac Sync to verify that the sync works correctly with the default bookmarks. If this works properly, replace the Bookmarks.plist file in ~/Library/Safari with the original file you placed on your desktop.
3. Create a folder on your desktop named Bookmarks.
4. Open Safari and go to Bookmarks > Show All Bookmarks. Note the different sections of this window.
Collections - Found on the left side, this contains the groups of your bookmarks, such as the bookmarks that reside in the Bookmarks Bar or the Bookmarks menu.
Bookmarks - Found on the right side, this section contains headings for Bookmark, Auto-Click and Address. We will call this the Bookmark section.
5. Click the different Collections to see how the Bookmarks change with each Collection.
For each Collection that has Bookmarks entered into it, create a corresponding name in the Bookmarks folder you created on your desktop in Step 3.
Position the Finder window--where the bookmarks were created--next to the Safari window so that both can be seen on the screen at the same time. The best position is to have the Finder window on the left and the Safari window on the right.
For example, the Bookmarks folder on your desktop will probably contain the following folders:
Bookmarks Bar
Bookmarks Menu
Address Book
History
All RSS Feeds
and any others that have content
6. Within Safari, select the Bookmarks Bar collection from the Collections section. The bookmarks contained in this collection will appear on the right.
7. Select the first bookmark on the right, and then press Command-A to select all of the bookmarks.
8. Drag all of the selected bookmarks to the Bookmarks Bar folder in the Finder window. Next, delete the selected bookmarks in Safari by pressing the "delete" key.
9. Keep repeating steps 6 through 8, selecting different collections, until you have copied half of your bookmarks to their corresponding folders in the Finder window and subsequently deleted them from Safari.
10. Open the .Mac System Preferences and click the Sync tab. Deselect all items from the Sync tab except for the Bookmarks. Try to sync. If syncing is successful, go to step 11. If it is unsuccessful, skip to step 13.
11. You now know that the second half of your bookmarks is able to sync normally. Therefore, the problematic bookmark must be in the first half of your bookmarks. Delete all of the bookmarks in the remaining collections in Safari. There is no need to copy them to the Finder window.
12. Select the bookmarks from each folder in the Finder window, and drag them back to the corresponding collection in Safari. Then try to sync your Safari Bookmarks again.
13. If the issue occurs with this set of bookmarks, remove the bookmarks from half of the remaining collections and sync again. Repeat these steps until you have isolated the problem bookmark to one collection.
14. Once you have isolated to one collection, start removing bookmarks from the affected collection. Alternately, sync and add/remove the bookmarks until you have narrowed down the problem to one bookmark.
15. When you have isolated the problem data, please copy this link into your response to this email. Also include the name of the bookmark as it appears in the Show All Bookmarks window.
After you have identified the Safari Bookmark that prevents a successful sync, replace the Bookmarks.plist file in "~/Library/Safari" with the one in "~/Library/Safari Copy". Next, find and delete the bookmark you have identified as problematic."
