Video problem after updating to 10.6.4

I have a Macbook Pro 15" 2.2ghz intel core 2 duo, 2gb ram, GeForce 8600M GT running a 30" Dell 3007WFP LCD on Snow Leopard.

After updating to 10.6.4, anything I put on the far left hand side of the screen is showing up on the far right hand of the screen, it's an area 3" wide and as tall as the monitor. It's like it's a mirror image on the area of the right side of the screen. I tried to take a screen shot, but it doesn't show up for some reason. Anyone have a clue on how to fix this?

Try going to /System Preferences/Displays and clicking on "Detect Displays." Maybe that will help. Also, try putting the Mac to sleep while the display is on, then waking it back up. I have to go through the sleep/wake up routine every time I switch from laptop use to my big external monitor in order to get the proper resolution on the big screen.

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I thought maybe that was the problem so I tried all of that but it never fixed it. I noticed it's doing this with resolution 2048x1280, 2048x1536 but anything higher or lower works normally.