No. 64-bit will not work at present. Parallels is only a 32-bit application, so it only virtualizes a 32-bit processor.
That also means that if you install a 64-bit version of Vista on Boot Camp (which is hard enough, considering Apple only provides 32-bit drivers,) you will *NOT* be able to use Parallels' Boot Camp option, even when they add it for Vista. (Much as you presently cannot for XP 64-bit, while you can for XP 32-bit.)
I can confirm that Ultimate 32-bit Retail works just fine, though.
Last edited: Apr 11, 2007