reassign 983357 linux severity grave thanks I rebuilt the iso using the version of isolinux from stable and it still crashed the domU. When I rebuilt it using the vmlinux and initrd.gz from the stable iso, it successfully boots, so it appears to be caused by the kernel.
Interestingly, there appears to be a different kernel build just for use under xen in install.amd/xen and using that one also works. Maybe we need a menu option in isolinux to load that kernel instead?