This is similar to the second problem, except that a sysdatabases entry does exist, and the sysusages entries are apparently correct, but are not complete because the end entries have been overwritten by subsequent database creation/alteration.
Symptom 1: A database exists that should not be present.
Symptom 2: Attempting to work in the database generates 806
errors, "Could not find virtual page for logical
page n in database <dbid>."
Corrective Action: Delete the sysdatabases entry and all sysusages entries for that dbid.
