I have 2 ~2 year old Apple 24" LED LCD's running on my 12-Core Mac Pro. Recently one dropped brightness levels periodically, even shutting off completely. During a genius appointment, the same display acted in the same manner running off an in-store MacBook Pro with 10.8.2. The tech and I both agreed it must be power supply related as the backlighting seemed fine in checks. Having moved, I postponed fixing it until settled. Suddenly, both displays began showing the same behavior. I was able to attach them to my Mac Pro without the USB/Mini-display port extension cables, and it seemed to make a difference. However, I've noticed flickering from time to time. I installed "Snow Leopard", and haven't experienced these issues in 10.6 or Windows 7 64-bit. Not once in a few weeks. This leads me to suspect 10.8.2 is the cause. Anyone with a similar setup experiencing this phenomenon?