In my reminders window, all task reminders tell me that they are due at
17:00, no matter what the time the reminder was actually set for.

This means that a reminder for a task set to go off at 3pm will come up and
the entry in the "Due in" column in the reminders window will show "2 hours",
when actually it is due now. When the time is 4pm, the "Due in" column will
show "1 hour", even though it is 1 hour overdue.

If I single click on the entry, the additional detail comes up at the top of
the reminders window, stating the task name and "Due: 19 October 2008 17:00".
However, opening the item shows the correct reminder time of 15:00, and
viewing the reminder time field in tasks view also shows the correct value.

The same occurs with previous days' tasks - a task for 3pm yesterday would
show up as 22 hours overdue at 3pm today, as it claims to have a reminder
time of 17:00, until you open the item.

Calendar items appear correctly, though.

Can anyone help to correct this?

I'm running Outlook 2007 on Vista Home Premium, using a local .pst file. I
dismissed all of my existing reminders, restarted Outlook, then restarted
Outlook in safe mode (twice) and have determined this behaviour by using a
test task and appointment (in safe and normal modes). I use Nokia PC sync to
synchronise with my Nokia N95, though this hasn't been running while I have
been testing.