Computer monitor SD problem

Hi, I have a PS3 connected to a Samsung Syncmaster 953 BW with a HDMI-> DVI cable. The problem is that when I try and turn the PS3 to standard definition (need SD due to gaming lag issues), it is fine until after about a minute then the monitor goes blank. I have to press the source button to get it back but then it will go blank again after a while. The monitor works find when in HD such as 720p.
I am pretty much a novice when it comes to this stuff so I have no idea what the problem is. Any help would be very much appreciated, thanks .

That monitor is a computer monitor not a TV.

Have you checked all the PS3 setting to make sure it is setup correctly for SD. What settings are you using on the PS3?

There is a menu option on the monitor that you can go into to see what resolution the monitor is getting (or sometimes when you first switch to a new input). What information does it display for you when you have the PS3 in SD mode? (maybe this mode is not fully supported in the monitor).

I am not a PS3 person but another option is if you can set the render options lower if it is not keeping up for game play.