Recently I've been getting screen tearing issues while playing; it happens in Firefox and Chrome and it's always where the red line is in this picture: http://i.imgur.com/Gsu5x.png
Yes, it's an artificial line and the machine is dual-core. It just started showing up over the past week or so, so I wondered if something had changed. Thanks!
If you had a quad core, you would see vertical tears too. It's parallel rendering. Single core machines don't see tears, but they render more slowly with more CPU. Take your pick! ;-)