Hi Folks, I originally started thinking this was a kernal issue, but now I''m wondering if it''s a hypervisor issue, so... I have an old tower machine - a homebrew that I use as a sandbox. Just loaded it up with a copy of Debian squeeze (amd_64), and the latest xen package - works fine, but... - shutdown -h works just fine - reboot goes down, gives the console message "restarting system", then hangs On an earlier installation (Lenny, x86 install) adding "reboot=bios", to the Linux Command Line options, solved the problem (suggestive of a kernal/acpi issue). This time around - 64bit image (amd64), squeeze, none of the reboot=[....] parameters seem to make a difference. (I note that the Debian installer documentation indicates that reboot=bios only works with x86 images). I also note that the system will SOMETIMES reboot properly, particularly if its been running for a while - suggesting that perhaps it only looks like the problem is in the kernel boot process, but rather in something else that''s running at a very low level.... like the Xen hypervisor. So.... Any suggestions? Any diagnostic suggestions to help narrow down where the hang is occurring? Other thoughts? Thanks! Miles Fidelman