Users have the ability to configure table and seat arrangements for halls used by events that can then be assigned to specific registrants of the event. In this scenario users find that cancelled registrants show up as records that can be added to these seats and are able to assign them. Users feel these types of registrants should be excluded.
Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.