Problems with 2.6.6 custom kernel and Open Firmware

[Sebastian Tennant <sebyte@smolny.plus.com>]

After selecting its label in yaboot stage 2, my self-compiled 2.6.6 kernel,
(gcc-2.95, make-kpkg, dpkg -i, based almost entirely on the config from my stable
2.4.18 kernel), hangs in Open Firmware with the following message:

     "...ok
     opening display /pci@0000000/ATY,BlueStoneParent,Bluestone_B... ok
     copying OF device tree...done
     calling quiesce ...
     returning 0x01400000 from prom_init

     DEFAULT CATCH!, code=300 at %SRR0: 01403d3c %SRR1: 00083030

     Apple PowerMac3,5 4.3.3f2 BootROM built on 12/21/01 at 14:13:01
     Copyright 1994-2001 Apple Computer, Inc.  All Rights Reserved.
     Welcome to Open Firmware, the system time and date is: blah...

     To continue booting, type "mac-boot" and press return.
     To shut down, type "shut-down" and press return.

    Release keys to continue!_"

Any ideas why?

TIA

sebyte

G4 'Silver' desktop