So Mandriva can reboot fine. It is just when you power cycle that this happens. I've had this occur a few times when powering up, and unplugging a usb device allowed the booting to continue. In my case it seems like a usb problem, possibly with the usb devices themselves, but I don't know for sure.
In your case I wonder if it is ACPI or PNP related. When you perform a warm reboot, I don't think that IRQ numbers are assigned the same way as happens when you cold boot.