Hey Conny. My Ubuntu One client seemed to start connecting and working again this morning. I did a few syncs with Tomboy on my laptop and it seemed to work.
I then tried syncing Conboy (0.6) on my n810 to see what would happen. New error message now, so I thought I'd post it for you. -------- Synchronization Failed Error Message was: Expected sync rev (35) and actual sync rev (34) are not the same ------------- I thought I'd try to re-authenticate Conboy in case that was causing the problem. Same error (with the same sync rev numbers) came up. Hope this helps.