I dont know if this would help you guys much, depending on how similar setup the 8330 and 8520 are...
I found my girlfriends Curve 8520 kept rebooting randomly and would reboot when she put it down sometimes. Sometimes during reboot it would get halfway and reboot again.
Inevitably, she was sick of it to the point she was going to smash it against the wall.
So I suggested she let me open it up and have a poke around inside.
When I took the battery cover off to take the battery out I noticed that the battery didn't sit snug inside and was able to move around a little, which reminded me of when I had a Sony Ericsson K850i that suffered the same problems of random reboots which was down to poor contact from the battery to the motherboard.
So I opened it up and got the back of the housing off and saw there was rubbing where the contacts met with the board.
So I got a precision screw driver and bent the contacts from the housing to the board out a little so it would make better contact with the board and the same for where the battery would meet the contacts in the housing.
Then reassembled it and just to make sure the battery wouldn't move about, I wedged a bit of folded cereal box at the top of the battery so it would stay in firmly.
Ever since that 'Quick Fix' it hasn't rebooted once, even when slammed down or dropped.
I did this same quick fix to another 6 Curve 8520's with the same outcome
Hope this helps...