One thing that would cause the multiple MAC addresses could be connecting using both wireless and through a wired connection.
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this is exactly my own problem too...i make use of vista (ultimate) each time i reboot...WA validation tool kit requires activation and i make use of my personal broadband i don't make use of wireless or other access to the internet...i always use one method to connect...so i don't know if my mac address do change or not at this moment...anytime i want to use WA validation tool kit i will activate it and try as much as possible not to reboot my system for as long as my system can take...i know this is just a temporary solution but am hoping to get a permanent solution some day...