To see whether my G4 booting problems were down to some partition table 
error (disklabel was giving a couple of odd partitions), I took a second 
disk of which I cleared the start with dd if=/dev/zero and did an 
installation from scratch. It manually boots fine now. I've set 
boot-device (hd:ofwboot.xcf), boot-file (hd:3,/netbsd) and boot-command 
(boot). If I stop in OpenFirmware and type boot it works fine, but if I 
try to get it to boot automatically, it hangs at a white screen. Any 
ideas?

-- 
Stephen