Could it possibly be the option key itself? Set up a custom keyboard shortcut on the Mac OS X side, and see if it works. Do the same on the Windows end. Come to think of it, that may not be a good test because the option key being recognized is part of the bootup process not tied to the OS...Another thought, since I'm putting myself out here, was that maybe a firmware password was set but then you'd get a padlock icon with a field to enter in the password to proceed...I think I'm just rambling now...someone put me out of my misery