basically it just doesnt read some discs, some of the time, which is really irritating. anyone got any ideas? its a good 4 years old but even so.. it was chipped when i bought it and plays all regions fine. lately however some discs it just wont play. after the thing has been on for a couple of hours and is hot it sometimes improves. could the laser have become mis-aligned or something? or is it something to do with the way some discs are produced?