Probably it has nothing to do with the problem, but you never know...
I stumbled across some information concerning rebooting with the A20 gate
disabled (it may ditch the machine). Does the kernel do anything with the A20
line before rebooting? (Sorry, don't have the source code here)
See:
http://www.x86.org/Productivity/A20Reset.html
-- Ronald Hesper <hesper@phys.rug.nl> Departement of Solid State/Surface Physics University of Groningen The Netherlands