My files on the server don't disappear!

My used space on the server doesn't disappear as I want!
I tried Ubuntu One and had some trouble with some files.
I completely removed and reinstalled the Ubuntu One client software on my systems and deleted all the files on the server via the web-interface.
I also deleted my two (=all) computers from my Ubuntu One account (several times). After a period of days, there still is used space on my Ubuntu One account, and, says the web-interface: "You are currently using 152.6 MB of your 2.0 GB available for synchronized data. " (Should be an emty account!)
'View all files' --> 'No files' (and no notes and contacts added by me).
'View the machines connected to this account' --> 'You haven't added any computers or devices to your Ubuntu One account.' (They are gone as they should).

Why is there a used space left? I think there is some files there making trouble for me, when trying to use Ubuntu one. Some files and folders sync- some don't.