How to clear the red icon at the bottom right of the clock
Simlar problem to yours. But he never responded.
Removing the battery, with the power on, for 30 seconds, IS a hard reset.
If you look at the calendar in different views, say Day view, do you not even see the little alarm clock icon in the time slot when the alarm activates?
Have you looked in all calendars on the device?
All I can think of is clear the calendar database on the handset and then re-sync. Or else restore the calendar from a backup.