Try removing psmouse module from the kernel before halt nad reboot (add 'modprobe -r psmouse' to halt and reboot scripts) - that fixes a lot of ACPI problems.
-- Screen reactivation fails on HP nx6325 https://launchpad.net/bugs/68062 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
