Xen 40_custom tested OK with xen-4.1.1-rc1-pre.gz in Lucid

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry "Ubuntu, Xen 4.0.1 dom0 2.6.32.40-pv" {
   recordfail
   insmod ext2
   set root='(hd0,3)'
   search --no-floppy --fs-uuid --set 8b1da4ef-6f52-4c40-affd-0a4abd5e364c
   #multiboot (hd0,3)/xen-4.0.1.gz ro noreboot dom0_mem=512M dom0_max_vcpus=1 com1=115200 console=com1,vga
   multiboot (hd0,3)/xen-4.1.1-rc1-pre.gz dummy=dummy ro noreboot dom0_mem=1024M dom0_max_vcpus=1 com1=115200 console=com1,vga
   module (hd0,3)/vmlinuz-2.6.32.40-xen-pv dummy=dummy root=/dev/sda5 ro console=hvc0 console=tty0 xencons=hvc
   module (hd0,3)/initrd.img-2.6.32.40-xen-pv
}