Hi,

> # fdisk sd0
> NetBSD disklabel disk geometry:
> cylinders: 57272 heads: 32 sectors/track: 64 (2048 sectors/cylinder)
> 
> BIOS disk geometry:
> cylinders: 1024 heads: 255 sectors/track: 63 (16065 sectors/cylinder)
> 
> Partition table:
> 0: <UNUSED>
> 1: <UNUSED>
> 2: <UNUSED>
> 3: sysid 169 (NetBSD)
>     start 64, size 117292992 (57271 MB), flag 0x80
>         beg: cylinder    0, head   1, sector  1
>         end: cylinder  951, head  31, sector  0

Hmmm, start 64 is a bit weird indeed, should normally be 63.
Flags 0x80 is good, for it means is the active partition.
Could you try to do: fdisk -u sd0 ?
And then not changing the idea of what the bios thinks,
Then ... The data for partition 3 is: 
....
Do you want to change it? Then type yes.
Do not change sysid, start and size and do not explicitly specify begin
and end address. See what it comes up with, write the table.

After that you could try: fdisk -i -c /usr/mdec/mbr_bootsel sd0
then fdisk -B sd0
Reboot, though, since netbsd is the only partition you shouldnt need this.
fdisk -i should suffice, try it out after the -u operation.
But you could try the above.
Bye,

Mipam.