Chances are very good you need to clean the laser as opposed to cleaning the discs. Don't waste your money on a cleaning disc. You need to CAREFULLY clean the lens with a Q-TIP and either a delicate parts cleaner (without lubricant additives!!!!!) or just barely dampened with isopropyl alcohol. Be careful when disassembling as there is a flexible ribbon that joins the lid to the base. If this doesn't fix your problem, then you probably need a grating alignment or have a bad laser. Either way, at this point I'd recommend you take to a trustworthy servicer.