oster@cs.usask.ca said:
> Intel released a microcode patch that apparently fixes some TLB 
>  issues in certain Core 2 Duo CPUs

Thanks -- they are not eager to announce it publically
as it appears.
Just found a new BIOS on the Dell website, marked "urgent"
(but one has to search for it).

ad@netbsd.org said:
> Adding a tlbflushg() in pmap_destroy() is a workaround. Matthias
> Drochner tested this and it's confirmed.

Yes this helped. I've just flashed the new BIOS and removed
the tlbflushg() -- seems that the problem is gone.

best regards
Matthias