General :: Touchpad Sensitivity Scales To Virtual Screen Dimensions?

I am experimenting with attaching a second monitor to my Ubuntu Natty laptop, and I have noticed an annoying "feature" that makes any multi-monitor setup so unusable that I actually prefer my single-monitor laptop setup. It appears that the system automatically "scales" the X- and Y-axis sensitivity of the touchpad to match the dimensions of the "virtual" screen that spans across multiple monitors. This is best illustrated with an example. If I set up two monitors side-by-side, the touchpad's X-axis speed is doubled, so that moving my finger the same distance on the touchpad causes the mouse on the screen to move twice as far in the X direction as it did when I had only a single monitor. Yet the Y-axis sensitivity remains unchanged, so all diagonal mouse movements end up at the wrong angle. This makes the touchpad almost completely useless, since the mouse on the screen does not move in the same direction as my hand on the pad.

Is there anything I can do about this? I just want the X- and Y-axis speeds to be identical, and I definitely don't want my mouse sensitivity changing because I added a screen. The touchpad is a Synaptics touchpad, by the way. The laptop is a Dell M1330 with an nVidia graphics card.