Hmmm... well that is a subtlety to your setup I had missed. You have a single Core processor in your Core/Hybrid but a dual-core in your MD. At present whatever kernel you choose in the initial Debain part of the installer is the kernel that will be used for all PLuto MD's too. It might be possible to update the kernel post install of the MD... but I have not tried that and i would not recommend it to you.
So you could try this... re-install again and this time select the smp kernel on your single core machine... this should work in my experience. Then when you add your dual core MD it will get the smp kernel and then hopefully it will boot ok.
I cannot install the smp kernel on my single core machine, it crashes everytime when it starts installing the kernel.
Anyway I found in /tftpboot/pxelinux.cfg the following:
APPEND root=/dev/nfs acpi=off vga=normal initrd=default/initrd.img-default-126.96.36.199-pluto-2-686-smp ramdisk_size=10240 rw ip=all ydebug apicpmtimer
Obviously it boots the smp kernel by default?
I will try to contact one of the pluto guys again...
thanks for your help.