Upgrading 3.0.1 to 4.0 on IP22

[Stephen Borrill <netbsd%precedence.co.uk@localhost>]

I'm trying to upgrade my Indigo2 to 4.0_STABLE from 3.0.1, but I'm unable 
to get it to boot any netbsd-4 kernel successfully. The bootloader makes 
all the right postures, but then the screen blanks and no boot messages 
appear. I am unable to get a response from the keyboard (Caps Lock, etc).

The machine is booting from its HDD (not network boot) and I'm using a 
glass console, not serial.

I'm trying to boot using "boot /netbsd4" where /netbsd4 is un-gzipped
netbsd-GENERIC32_IP2x.gz. I've tried INSTALL and GENERIC kernels and ELF 
and ECOFF kernels.

Should the 3.0.1 bootloader happily boot 4.0?

Any other gotchas I am missing?

--
Stephen