The various vague descriptions of the bug all point to an 8-bit event counter in the firmware. Whenever the events it has been counting hit the wraparound point, it becomes toast and never boots again.

But this only happens if the system is rebooted or shutdown (one, the other, or both.. I forget), at an instant when that particular event counter happens to have the magic number in it.

The events that trigger the counter to be incremented sound like they are slow events .. like daily or something. But after a while, it becomes a bit of a crap shoot as to whether your next reboot/shutdown coincides with the bad counter value.

Good luck.