I have installed Debian 6.0 Squeeze (current stable) and Debian 7.0 Wheezy (current testing) in Fusion 5.0.2
Both work out of the box with 3D accel enabled.
So I was thinking that the problem may be in libmesa 9.0, version provided by ubuntu 12.10.
Debian 7 provides mesa 8 and Debian 6 uses 7.11 (or something similar, I'm at work and my mac is home).