IVB uses session data to store last visits. It is trying to access the session table to find an entry, then delete row and insert a new row listing the latest visit.
You have a problem with IVB connecting to the SQL database.
Either the db has got corrupted, the db server is offline, the db authorisation has changed (and your haven't updated your config to reflect the change) or the whole db has died a death.
Id place my bet on the db server being offline or the db is corrupted
Check with your host