This morning all of our Office 2010 installs received this message (and was no longer syncing). After restarting those instances, they all seem to have begun syncing and sending/receiving properly (although the error message still pops up upon startup).
However, our Office 2007 installs all sit at "Disconnected" regardless of whether they were restarted or not. All are able to access OWA properly so it doesn't appear to be a login issue (although all of them get prompted for a login/pass when restarting Office 2007). Don't see anything regarding it on Office365 Twitter.
