the viewable picture has shrunk in from the left and right (but not from top to bottom.) I would love to keep using this, but the picture really is distorted enough to be a problem..

Click to expand...

Isn't that lovely? I had the exact same problem after having a 20" ColorSync for a month, and had a devil of a time finding the solution.

Try, if you can, to switch to the lowest resolution/refresh rate that you can. That's the work-around for my display. I have to use it at 60Hz. Otherwise, you'll have to open it up and do some solder work.