Laptops :: MacBook Pro And Samsung Monitor - Quit QuickTime

I've been using my 15" MacBook Pro (purchased late 2009) running 10.6.5 with a very old 23" Apple Cinema Display for a year now with no problems. I use both the laptop screen and the external monitor at the same time. Recently I tried switching to a Samsung SyncMaster 245BW since the Cinema Display is starting to show its age in terms of picture quality. Everything works fine until I launch QuickTime or any application that uses QuickTime (iTunes for example). This causes the Samsung monitor to jump back and forth very quickly from a screen full of snow to a normal screen over and over and over, rendering the external monitor useless. The only way to get it to stop is to quit QuickTime, unplug the external monitor, and plug it back in.

The same thing happens when I try switching external monitor resolutions from 1920x1200 to anything else. The only refresh rate available is 60hz. All others are grayed out. My MacBook Pro apparently has just one graphics card since the energy saver preferences don't include the option to switch between better graphics and power saving.