Hi Kai,
This would normally happen if there was a DB that no longer existed. If you went into your selection list, and switched to text view, it would show the DB mentioned as having failed. You would then simply delete it from there, and your backups would succeed.
IN this case, it seems like your agent might be corrupt, or your licensing isn't correct. I would suggest the following:
1. Restarting the RAWS agent on your server (assuming it is a remote server), and checking to make sure it is publishing to your backup media server.
2. Check to make sure your license is installed. Help --> About --> License Information.
3. If that fails, look at uninstalling the Remote Agent, and then do a push-install again.
I take it your permissions to the server and Exchange are correct?
Laters!