The N900 is restarting itself AGAIN! :(

Question

I am sorry for posting this again but the problem "is back" even that I did the ECHO fix my N900 again is rebooting itself
It worked great like for 3 hours but I left alone the phone for 30 minutes (aprox) and when I tried to use it again it rebooted.  An hour has passed and it has rebooted itself 4 times....
I'm now really upset since I feel like Nokia ripped us all off, since this is not a problem that it is only happening to me but to a lot of people!!
Any other suggestions on how to fix this will be appreciated please!
Thanks

Answer 1

I know I have been nagging everyone with "sim cards", "WiFi"...etc.  So if we are back to square 1 can we use this group to do and experiement? 
First lets just look at the device as a phone.  I know that a fair bunch of the telephony code way ported/modeled on the Symbian subsystem.   I also know that this re-booting has been seen on a few Symbian devices- because the telephony subsystem is very closely integrated with the Power management subsystem and the Telephone subsystem has the function to put the device in power saver, shut down the phone...etc.
Test Case:1
1) Settings-> time and date-> disable update automatically.
2) power cycle device.
3) Use for at least 8 hrs if no reboots
4) report findings.  
Test Case 2
1) Test case 1 configuration in place.
2) Remove all wifi points, disable network searching or switching.
3) Manually select carrier from Settings->Phone-> network.
4) In Network mode select GSM
5) use for at least 8 hrs if no reboots
6) Report findings.
After this we move on to two more test cases.