[...]
> Oh, I know this, I had the same problem some time ago.
> 
> I think this happens when the bootblock on a harddisk is trashed in a very
> weird way.  It doesn't matter, if you want to boot from this disk or not.
> Because of this I needed *AGES* to find that out.
> 
> Overwriting the bootblock with a fresh one (with fdisk(8)) fixed it for me.
> (But I still don't know, how the bootblock got coruppted).

Nope.
It refuses to boot anyway.

[...]

> Ok, it boots now. Fine. Don't touch the bootblock and just "adjust" the
> size of your disklabel and enlarge the size of the last partition (you
> will loose everything in that partition) or make a new one for the rest
> (use disklabel  -e -r [-C] disk for this).

So: I install from scrach NetBSD 1.3.2 [who says 8 gigs hd], then update
to 1.4.1, then updated the disklabel extending the last partition,
newfs'ed it, rebooted, repopulated with the /usr contents (I did
reistall sets), rebooted and.... it stops saying "3." 
Then I scream to my monitor what I was thinkin' about and gone bed.

a)
NetBSD 1.4.1 (GENERIC) #1: Tue Aug 10 00:03:09 MEST 1999
    fvdl@struis:/usr/src/sys/arch/i386/compile/GENERIC
cpu0: family 5 model 4 step 3
cpu0: Intel Pentium/MMX (586-class)
real mem  = 33161216
avail mem = 27222016
using 430 buffers containing 1761280 bytes of memory
mainbus0 (root)
pci0 at mainbus0 bus 0: configuration mode 1
pci0: i/o enabled, memory enabled
pchb0 at pci0 dev 0 function 0
pchb0: Intel 82439TX System Controller (MTXC) (rev. 0x01)
pcib0 at pci0 dev 7 function 0
pcib0: Intel 82371AB PCI-to-ISA Bridge (PIIX4) (rev. 0x01)
pciide0 at pci0 dev 7 function 1: Intel 82371AB IDE controller (PIIX4)
pciide0: bus-master DMA support present
pciide0: primary channel wired to compatibility mode
wd0 at pciide0 channel 0 drive 0: <QUANTUM FIREBALLP KA18.2>
wd0: drive supports 16-sector pio transfers, lba addressing
wd0: 17624MB, 16383 cyl, 16 head, 63 sec, 512 bytes/sect x 36094464
sectors

              ^^^^^ does not match with sects #

wd0: 32-bits data port
wd0: drive supports PIO mode 4, DMA mode 2, Ultra-DMA mode 4, Ultra-DMA
mode 3, Ultra-DMA mode 2
pciide0: primary channel interrupting at irq 14
pciide0: secondary channel wired to compatibility mode
atapibus0 at pciide0 channel 1
cd0 at atapibus0 drive 0: <TOSHIBA CD-ROM XM-5402TA, 8500734693, 3045>
type 5 cdrom removable
cd0: 32-bits data port
pciide0: secondary channel interrupting at irq 15
wd0(pciide0:0:0): using PIO mode 4, Ultra-DMA mode 2 (using DMA data
transfers)
cd0(pciide0:1:0): using PIO mode 3
[...]
boot device: wd0
root on wd0a dumps on wd0b
root file system type: ffs

b) The corrected(?!) disklabel
# /dev/rwd0d:
type: ST506
disk: mu
label: 
flags:
bytes/sector: 512
sectors/track: 63
tracks/cylinder: 16
sectors/cylinder: 1008
cylinders: 35808	<-this was 16383!!!
total sectors: 36094464
rpm: 3600
interleave: 1
trackskew: 0
cylinderskew: 0
headswitch: 0		# milliseconds
track-to-track seek: 0	# milliseconds
drivedata: 0 

8 partitions:
#        size   offset     fstype   [fsize bsize   cpg]
  a:   263088       63     4.2BSD     1024  8192    16   # (Cyl.    0*-
261*)
  b:   525105   263151       swap                        # (Cyl.  261*-
781)
  c: 16514001       63     unused        0     0         # (Cyl.    0*-
16382)
  d: 16514064        0     unused        0     0         # (Cyl.    0 -
16382)
  e: 15725808   788256     4.2BSD     1024  8192    16   # (Cyl.  782 -
16382) <- blocks recalculated by hand excluding some of the last cyls

Hope this help a little more.

Marco/Vor