I was looking for something similar for a fault like that on an XP system Dave.
From what I can find out its an MBR problem, XP tends to repair any corrupted or damaged files on subsequent reboots, not sure if ME does but it sounds like by running Scandisk that sorts it on yours.
Does ME have a repair MBR facility ?
If it does if you run that it should hopefully cure the problem, if not try running something like Nortons WinDoctor