I have set up a task with a trigger at 7:00am each weekday, repeating every 3 hours for 12 hours:

The problem is that Vista seems to ignore the 12 hour limit, and runs the task every 3 hours, 24 hours a day, 7 days a week. The task runs successfully, but I am confused as to why the scheduler is ignoring the duration...
Does anyone have a suggestion as to what I might be doing wrong, or is this a bug in the task scheduler?
Cheers,
Ash