I stumbled into the same problem a while ago. While I did not use a hardware debugger I used the sample demonstrating serial output to find that the Montavista kernel stops at the rfi instruction which is used to simultanoeusly turn on instruction and data address translation and to set the instruction pointer to the (remapped) start_here label. Unfortunately I lost my PPC hardware (405GP Walnut board) before I could find any solution.
Regards Tom ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
