"In all my years of working with Linux I don't think I've ever met up with someone having as many problems with a Linux distro as you have!!!!! "
Agree. And the failures seem to occur in a rather un-Linuxy way.
"And it is extremely rare to see a Linux distro crash either itself or the system hardware."
What usually happens when it does is that a process locks up or the X-server crashes. Fix by ending process or restarting x-server. Full blown kernel panics are unusual. Never known a Linux distro spontaneously reboot, that's Windows type behaviour.
I suspect either a troll or a duff motherboard (Memtest only tests memory, not other components).
Mac