The way to fix this is canned air. What you do is buy a bottle of canned air, open the UMD tray, and gently spray the air into the tray. Be sure to hold the can at least 3 inches away from the open tray, and also make sure to hold the can upright. If you hold it upside down you will get a super cooled liquid coming out instead of air. Which could quite possibly harm your PSP. (I looked it up).