Had the same problem after updating to El Capitan, but only on the IMac of my wife not on the MacBook Pro, both early 2011.
after reverting all this threads I had fear to loose everything, finally I found the following which worked perfectly without loosing anything.
This this will help you too!!!!
Back up all data.
Triple-click anywhere in the line below on this page to select it
~/Library/Application Support/SyncServices
Right-click or control-click the line and select
Services ▹ Reveal in Finder (or just Reveal)
from the contextual menu.* A folder should open with an item selected. Quit the application if it's running. Move the selected item to the Trash. Relaunch the application and test.
*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination command-C. In the Finder, select
Go ▹ Go to Folder...
from the menu bar and paste into the box that opens by pressing command-V. You won't see what you pasted because a line break is included. Press return.
Have success
Reg
Montesa8