Is there something special I need to do to be able to use external LCD displays with my new MacBook Pro? Do I need extra software, or do I possibly need a different cable?

I'm attempting to use an external display with my MBP. I've got a "Mini DisplayPort to VGA Female Adapter for Mac", plugged into the thunderbolt port on my MBP, which I understood should be compatible with thunderbolt. I've tried this with three different SyncMaster models: a B2330 (21.5"), a EX2220 (22"), and a third (also 22" ish) which I don't have the model # for -- but all are 1920x1080 resolution; plus an additional HP monitor of similar size and resolution.

In all four cases, the MBP recognizes the screen and choses the correct resolution. However, the display is shifted over about 1 inch. This is true no matter if I change screen resolutions also. The controls on the monitor for horizontal position don't help. Also, sometimes (especially if I drag an app over into the second screen), the screen starts skipping left to right and having bands of fuzz. Additionally, the monitor will periodically blink off for a moment, trying to switch from Digital to Analog and back (the Syncmaster shows text on the screen to tell you it's trying to do this). Often when it comes back from one of these blank-outs, it will show OK (no skipping or fuzz) but still shifted right; then after a few seconds it will go wrong again skipping and fuzzy.

This photo shows the worst of it. I've added red rectangles to show the physical edge of the screen, and a yellow rectangle to show the empty space on the left of the screen. (Sorry for the awful quality and lighting!)

Also, it's worth noting I am on Mac OS X 10.6.7, and yes I have this update 1.4 installed.