> I'm not sure exactly, but I noticed that it works fine if I don't load
> HIMEM.SYS.  I assume it has to do with putting the system into protected
> mode.  Dosboot runs gateA20(), but himem.sys allready has done that.

It fails if

 - you have any XMS memory manager installed (can't find enough ram),
   there is a patch in the gnats database and a newer version available
   at zelof1.zel.kfa-juelich.de:/pub/NetBSD/bootcode

 - you are running in V86 mode (emm386 or quemm or ....) - no chance to 
   get into protected mode and back without doing a lot of VCPI/DPMI
   hacking. I don't think this would be worth the work. This fails silently,
   as you described.

Otherwise, you should either copy your kernel to the dos partition and
say

 dosboot netbsd

or use something like

 dosboot -u sd0a:netbsd


Martin