I've a 6700 model and have been experiencing problems specifically with the alarm feature in to-do lists. My regular alarm works like a charm, but if I use the alarm feature for reminders, there seems to be a problem. Any time I add a note with a deadline, the note status gets correctly updated at the specified time, but the alarm doesn't go off until just after midnight (regardless of when I set the reminder for). However if I switch the phone off and switch it back on a minute or so after the reminder alarm is supposed to have sounded, the reminder does get activated.
As I said, my daily alarm clock feature works correctly, so it's not a problem with the system clock. Has anyone else experienced a similar problem before?