I think mike ment Greenscreen in DVD AND GAMES! Theres no doubt about it, that shouldn\'t happened.
HOWEVER in the options of the PS2 theres an option to choose Composite and RGB, if you select Composite whilst using an RGB cable then the screen will go green. So check that its set to RGB first.
Otherwise unfortunatly it is probly a duff PS2 because you would of thought that maybe sonys feature which turns the RGB Green screen on when detecting RGB cable is turning it on all the time rather than just for DVDs.
As for the Ps2 in second scart socket theres no point really, you loose the gain of RGB as mentioned so its just as easy to use the original cables supplied with the PS2.