Comment 5 for bug 138440

it seems I found the problem, and fixed it temporarily:
The reason ubuntu wouldnt boot with Hyperthreading enabled is because I had my new Belkin F5D7050 plugged in. http://catalog.belkin.com/IWCatProductPage.process?Product_Id=179211

When I unplugged this usb card I am now able to boot with Hyperthread, after I noticed that I decided to recompile my ralink rt73 wifi driver from http://rt2x00.serialmonkey.com/wiki/index.php/Downloads and plug my usb card back in.

Once I did this, all was fixed, I hope this helps developers fix this problem because gutsy and a few new releases are right around the corner