[otrs] Dynamic Statistic: Ticket Average stat produces 0

Hello All, When generating a stat using the Average Ticket Time option under Dynamic Objects for a few queues, the time results are always returned as "0" zero. It doesn't matter which of the available 9 calculations available are used, all produce 0. Other reports (ticket count, etc) are working ok, I only see the problem with the calculations using time. Is there a config item in sysconfig i've overlooked to activate that? I use OTRS 2.4.4 on Ubuntu 8.04.3 LTS using MySQL 5.0.51. Many thanks in advance for any useful Tipps. Thanks Mike James