External monitor troubles

Hello all,

I have a Samsung SyncMaster 2253BW 22" monitor and a 15" mid-2009 2.53 GHz MacBook Pro that I've been trying to use together via the VGA adapter. When I connect the two, the monitor is recognized by the OS and recognizes the computer, displays the image for about two or three seconds, and then disappears. This same cycle repeats every fifteen seconds, or so, no matter how I attempt to introduce the monitor to the system, either before startup, or after, or with either mirroring or desktop extension on. The monitor does work with an older 1.83 GHz MacBook also running Snow Leopard, so I don't think it's either the monitor or Snow Leopard entirely in themselves. I searched these forums, Apple's documents and manuals, and the Internet in general, and can't seem to find out what's wrong here. Do I need to use the DVI adapter instead?

 

I am using the 9400M. I have the general repair warranty still, but no phone support, which would be extremely handy, as I live a fair distance from an Apple Store.

 

I'm using a Mini DisplayPort to VGA adapter.

 

The support page seemed to be describing the problem I'm having, but, upon downloading, installing, and running the update, a pop-up announced not being able to find an adapter to update, despite it being plugged in securely, and the monitor on the other end. The webpage does say the update is for 10.5.6, while I am running 10.6.3. That surely seemed to be the way to go, unfortunately.