Comment 233 for bug 99508

I am giving a possible solution I just found.

Install Ubuntu Tweak, run it from Applications-Systme Tools-Ubuntu Tweak.
Click Desktop in the left panel and chose Window Settings in its sub-panel, then, on the right there are two slide bars, move the slider of the uper one, which stands for "Active window transparency level", to any where but 1.0, then hoover you mouse over the three in up right corner, see what.

I solved the problem in this way, but I don't know if this could work for you all. I'm using a Geforce FX5600 and driver 173.

If this also works for you, I suggest moving the second slider to 0.5 for that looks the best.