I am running 64 bit version of Vue 6 xStream on XP 64 on a dual 5160.

When you installed Vue on XP 64, it prompts you for either 32 bit or 64 bit.  I believe you can have both.

I am issues with Vue 6 xStream on my machine  - not sure if they 64 bit only problems.

   1. Floating license issue where it drop connections and readds it - A pretty annoying message comes up.  ( even happens with no scene loaded )

 2. Crashes on render some times - non responding and screen indicates 100%

I have contacted e-on technical support on both issue and quite serious speaking also.

Render speed is very fast because of 4 3Ghz Core 2 based cores on the machine, unfortunately reliability of the software is in serious question right now for me.

I have no such issues with Lightwave 9 64 bit on same machine.