compiz fails to start properly after update to 1:0.9.8.6+bzr3432-0ubuntu1~test1

Somewhere between compiz 1:0.9.8.6-0ubuntu1 and 1:0.9.8.6+bzr3432-0ubuntu1~test1 compiz broke on my VirtualBox VM running Quantal.

To reproduce.

Have a VM under Quantal which has the vboxvideo 3D passthrough driver installed.
sudo add-apt-repository ppa:unity-team/sru
sudo apt-get install compiz

(no need to upgrade everything, upgrading compiz is sufficient to cause the issue).

Restart.
Observe the launcher start but the session freezes shortly afterwards. I don't get the panel populated with indicators, and the desktop is unusable.

I can revert back to stock compiz with the following line which restores a working 3D (not software rendered) desktop.

sudo apt-get install compiz/quantal-updates compiz-core/quantal-updates libcompizconfig0/quantal-updates compiz-plugins-default/quantal-updates compiz-gnome/quantal-updates

When I try to report a bug against compiz it complains that a) I'm using software rendering, and b) it's not a valid package (sru ppa) for filing a bug against.

What changed in compiz between the above releases which regressed 3D detection?

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: unity 6.12.0-0ubuntu0.2 [origin: Ubuntu]
ProcVersionSignature: Ubuntu 3.5.0-22.34-generic 3.5.7.2
Uname: Linux 3.5.0-22-generic i686
ApportVersion: 2.6.1-0ubuntu9
Architecture: i386
CompizPlugins: [core,composite,opengl,compiztoolbox,decor,vpswitch,snap,mousepoll,resize,place,move,wall,grid,regex,imgpng,session,gnomecompat,animation,fade,unitymtgrabhandles,workarounds,scale,expo,ezoom,unityshell]
CrashDB: unity
Date: Wed Jan 23 13:59:41 2013
InstallationDate: Installed on 2012-06-28 (209 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha i386 (20120627)
MarkForUpload: True
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)