If you've read my thread about ActiveSync you'll see I've had a problem with this application hanging. One other thing's apparent: after resetting the phone (which lost all data - but a resynch later and it's OK - just got to reinstall all apps) - the battary started lasting overnight again.
It would appear that it's possible for a process to run, that isn't listed when you hold down the menu key, and for that to drain the battery down.
For the last two days the phone wouldn't make it through the night without discharging. This morning, however, it shows half charge.
Regards,
Slart.