> machdep.unaligned_print=1
> machdep.unaligned_fix=1
> machdep.unaligned_sigbus=0

thx for the fast answer, but it didn't solve the problem. After changing
this values the same thing happends. I recognized that this has been
already the setting of the values before issuing sysctl -f
/etc/sysctl.conf. 

This error:
ERROR: 1017  Can't find file: './mysql/help_category.frm' (errno: 13)
was due a wrong permission setting. chmod'ing mysql:mysql
/var/mysql/mysql/* did the trick.

Now everything works as it should, but the unaligned access error looks
pretty ugly and gives me a strange feeling, cause this should become a
production server... any other hints on this?

-- 
Regards
	/sp4rc