So you are using DVD-Rips.......
When using rips I would suggest using a very high quality cd-r since rips (most of the time) are harder on your laser.....
I personally use Verbatim Datalife CD-R's......
I would also suggest upgrading to a dvd burner (whenever your money permits

), because rips are becoming a thing of the past.....
Also, what version PS2 do you have....?
And when was the last time you cleaned the laser in your ps2?