I use U1 on Ubuntu 11.04 with no problems until today.
For the first time, I used Software Center's rating function and give 5 stars to my favourite paint application. I need to login before doing that, and I choose the email address used for my launchpad account (el.cameleon.1@...), which is dedicated to my activity on internet (forum, bugzilla, mailing list,...).
However, for my UbuntuOne account, I use another email address (my private one). I am not sure if it related, but I guess that login with my launchpad account disconnect me from U1, because now I have a message that tell me that I am not connected and to check my connection to the internet (which is fine, thanks).
Any idea? How can I log off in order to identify again into U1? Is it possibile to use one launchpad account for SoftwareCenter rating and another One for UbuntuOne?