"Henrik Steffen" <steffen(at)city-map(dot)de> writes:
> In my opinion, postgresql does something on my machine
> that leads to these complete system lockups.
Once again: postgres is an unprivileged application. It can *not* lock
up the machine that way. You're dealing with either a hardware fault
or a kernel bug --- evidently one that only appears under heavy load,
but that doesn't make it postgres' fault.
I'd suggest asking some kernel hackers for debugging help.
regards, tom lane