Well, I take that back. My phone rebooted once just recently this week. )-: Good news is that I seemed to have found out how to fix some of the random reboots through trial and error. I cannot guarantee that this will work, but many of them disappeared after I changed some settings and done some other stuff:
1) Format SD card in Windows (back up your SD card data first!) Make sure you format to FAT32. Don't try formatting it in Linux. I done this once and the phone wouldn't boot up!
2) Slightly overclocking prevents some freezes.
Under Settings > Cyanogenmod Settings > Performance overclock the max speed to around 1300-1400ish. This should speed the phone up, but not to the point of the thing overheating.
3) Fix SD Card permissions. Do this by booting into Recovery (You can do that if you have this ROM installed) and go to advanced > Fix SD card permissions. Now reboot.
4) Do not use Firefox, except the Nightly builds. Firefox has went through drastic speed and performance improvements recently, but the older builds, despite being called stable, are so slow, they will make the phone freeze and reboot. Yes, this includes Aurora.
5) Give the phone a break from time to time. After intensive gaming for hours on end, the phone will often reboot while exiting a game.
That's all the tips I have. I managed to drastically reduce my reboots by doing these, but not eliminate them completely. I hope g60madman or mantera find some hidden timeout value in the kernel (if one exists, like the auto reboot on BSOD in Windows) and either lengthens the timeout value or disables automatic rebooting so if this is a kernel panic, we may see the debugging details and upload them to fix some crashes.