Car wheels not turning only on x86 Windows Store build

I have a car, which has 2 wheels controlled via a script...the wheels turn, which moves the car.

This works fine in the Unity editor, on Windows Phone, and on Windows 8.1 (ARM, store app), and stand-alone web version, but doesn't work on Windows 8.1 (x86, store app).

Any ideas why this would behave differently in the x86 build? I don't even know where to look. Using breakpoints I can see that all my values are as expected. The code is below. The two wheels get the correct speed but don't turn (they are attached to the car by hinge joints). The is no conditional compiling of different code for different platforms. Debugging is Visual Studio doesn't throw any errors.

Code (csharp):

1.  
2.             currentSpeed = (-speed * signalStrength / 100) * directionMultiplier;
3.             motor.motorSpeed = currentSpeed;
4.             motor2.motorSpeed = currentSpeed / 1.5f;
5.             wheels[0].motor = motor2;
6.             wheels[1].motor = motor;
7.  

 

I will do that later today.

Here is a very similar (same?) case that someone else posted a repro for:
http://forum.unity3d.com/threads/246802-HingeJoint2D-ignores-motor-parameter-changes-from-script

 

Aurimas,

I submitted a bug report, and one of your colleagues responded very promptly to let me know the issue is fixed in Unity 4.5. I can't wait for the update!