Essexboy:
This is looking like a particularly intractable problem. I have been watching this thread with interest, as I'm experiencing precisely the same problem on a Win 7 laptop.
At this point, as you're deeply into differential diagnosis territory, I'm wondering if you would like a scan of any type from my computer so that you can do a side by side for common elements.
Let me know if so. Otherwise, I'll continue monitoring this thread in silent interest.
Regards,
Jim