I have been forced to move from a Centos Dom0 xen 3 Centos + Ubuntu Lucid DomUs To Debian Wheezy Dom0 Xen 4 Ubuntu Lucid DomUs However although I can create new DomUs on wheezy I cannot get them to boot. pygrub returns Error: Bootloader didn't return any data I have ensured that the disks are the correct way around in the xen.cfg and also that the grub config is correct. If I try to run pygrub manually eg /usr/bin/pygrub /dev/volgroup/disk I get Illegal instruction can anyone offer me any advice on this? Thanks Matt