I know this comes up every now and then, and usually is (suposedly) caused
by bugs in the firmware making it impossible to boot from some parts of
the disk - I've seen that before and always was able to recover by copying
the kernel(s) again.

This time it is pretty persistent:

Rebooting with command: boot
Boot device: /isa/ide/disk@0:\netbsd.aout  Arguments: 
Data Abort
ok boot disk:\netbsd.aout.old
DNARD Rev. 5, 08:00:2b:81:62:5e , 96 MB memory
Open Firmware  Built February 25, 1998 17:19:25
Copyright 1997 FirmWorks  All Rights Reserved

Rebooting with command: boot disk:\netbsd.aout.old
Boot device: /isa/ide/disk@0:\netbsd.aout.old  Arguments: 
[ Kernel symbol table missing! ]
Copyright (c) 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003
    The NetBSD Foundation, Inc.  All rights reserved.
Copyright (c) 1982, 1986, 1989, 1991, 1993
    The Regents of the University of California.  All rights reserved.

NetBSD 1.6ZF (DROWSY) #2: Sat Nov 29 18:02:52 CET 2003
	martin@night-porter.duskware.de:/usr/src/sys/arch/shark/compile/DROWSY


and I made sure the kernels end up early on the disk:

ls -lisa /netbsd*
 3 1512 -rwxr-xr-x  1 root  wheel  1539899 Dec 10 21:44 /netbsd*
 5 1424 -rwxr-xr-x  1 root  wheel  1447034 Dec 10 21:44 /netbsd.aout*
 7 1392 -rwxr-xr-x  1 root  wheel  1414744 Nov 29 18:23 /netbsd.aout.old*
11 1480 -rwxr-xr-x  1 root  wheel  1502937 Nov 29 18:23 /netbsd.old*

So, have I just been unlicky a few times in a row or is the -current kernel
realy broken?

Martin