In Console.App I can see various log messages. I've diagnosed a Time Machine problem and searched for "backup". In the resulting messages from backupd I also noticed the message
27/07/11 16.01.59,562 mds: (Error) Volume: Could not find requested backup type:2 for volume
showed up (which is most likely not Time Machine related but has the word backup in it).
Any suggestions on what this is and how I can fix it?