I know most people can run Vista-64 and Ventrilo, but I cannot.
Looking on the forums on the Ventrilo site, about 100,000 people cannot get this combo to work.
The ventrilo people were (at the point where I just decided to run Vent on my old XP system) stumped.
That was more then a year ago, but running it on my XP system which is 1 foot to the left works for me.