Bluehz+Openid created the issue

When synchronizing a folder, after synchronization if you attempt to synchronize that same folder again, the sync will fail unless you back out of the folder in the Open/Save dialog and re-enter the folder again.

For example - if I want to sync "Folder A"

1. Cyberduck> Synchornize
2. Open/Save dialog appears - choose "Folder A"
3. Complete sync
4. Return at a later date Cyberduck > Synchronize
5. Open/Save dialog open and remembers last choice "Folder A" - if you then attempt to sync the sync will fail.
6. In order to complete the sync you must back out of the selected folder in the Open/Save dialog (for example go up a level to the parent folder) then return back to the original "Folder A" in order to get the sync to complete successfully.

I have only tested this using Google Docs - but I assume it is generic bug that occurs regardless of source.