I have had similar reboots. but for now, no reboots since 3 hours and have played with my device the whole time. what I did? -disabled 3g -radio.(at last, did also numerous other tweaks that didnt help) that came to my mind when device rebooted in exactly same place where I once called with my E71 and the line was very distorted. and symbian nokias rebooting because of the 3g-gsm jumps have been normal before.

I am truly hoping that it would fix the issue. I'll create bugzilla entry tonight if there are no more reboots appearing.