New 31r1 install on G4 fails on reboot

[dlormand@aztecfreenet.org (DAVID L. ORMAND)]

I've installed 31r1 "Sarge" on a PowerMac G4 with a Sonnet upgrade.
The install seems to have completed without incident, but upon
rebooting, the machine locks up after starting the Linux boot,
with the following left on the screen:

pmac_init(): exit
id mach(): done
MMU:enter
MMU:hw init
hash:enter
hash:find piece
has:patch
has:done
MMU:mapin
MMU:setio
MMU:exit
setup_arch: enter
setup_arch: bootmem
arch: exit
openpic: enter
openpic: timer
openpic: external
openpic: spurious
openpic: exit

What has gone wrong, and what can I do about it?