New user of hesk so be patient please..

When I enable autoclose feature of the helpdesk, I cannot login to the helpdesk - when i disable it, I can. When in debug mode, I receive the following error -
Can't execute SQL: UPDATE `pwp_tickets` SET `status`='3', `closedat`=NOW(), `closedby`='-1', `history`=CONCAT(`history`,'
17-05-2015 16:35:05 | closed by (automatically)') WHERE `status` = '2' AND `lastchange` <= '2015-05-09 16:35:05'
MySQL said:
Out of range value for column 'closedby' at row 1
Please Help! I've left that feature off so I can login as far as fixing the issue - I've drawn a blank.