PS2 Slim Question

Lately whenever I've tried to play any dual-layer disc games like God of War and Gran Turismo 4 all I get is a skipping sound coming from my PS2. I've tried to clean the lens and even got out my old fat PS2 but still nothing. I also tried a brand new copy of Guitar Hero World Tour which is also a dual-layer disc and still the same result. Is there a way to fix this problem?

Here's a free repair guide download:
http://www.ebooksquad.com/search/PS2+slim+Repair+Guide+download

Repair video for ten bucks:
http://www.ultimateconsoleguides.com/playstation_2.htm