[otrs] Unlock timeout

Dear all, I have some point regarding configuration of Queue Ticket Unlock timeout setting to seek guidance, In the Queue setting it said "If an agent locks a ticket and he/she will not send an answer within this time, the ticket will be unlock automatically. So the ticket is viewable for all other agents." I had set it to 5 which suppose to mean after 5 minute the ticket should be unlock and the other agent shall able to see the ticket, but it seem to be not working! Is there any trick or step that I might miss out? Do I have to set up a cron job to unlock the ticket? I'm still on OTRS 1.3.2 on Suse 9.3 and Apche 2.0 Best Rgds Nuttapong