In the table USER_DATA there's a field USER_LAST_VISIT_TIME of type int(1). I didn't check the code, so this is just an assumption that it should be int(11).

Thanks Maze. A quick fix for that. This can be run from the control panel in the SQL Command area:

alter table ubbt_USER_DATA change USER_LAST_VISIT_TIME USER_LAST_VISIT_TIME int(11)