Well it looks like Cablenut does indeed work on Win x64
Here is my results from one of VanBuren's tweak settings:
http://ttester.broadbandreports.com/tweak/block:5563d9a?service=dsl&speed=3008&os=winXP&via=routerpppoe
And here are the results from my personal settings using Cablenut Live:
http://ttester.broadbandreports.com/tweak/block:27c09b9?service=dsl&speed=3008&os=winXP&via=routerpppoe