Recently, my Mac Mini is refusing to play DVDs. There were a few discs it would still play, but now it's refusing those too. Even DVDs that are brand new and just out of the case won't play, so I know the problem isn't the discs being dirty or scratched. When I insert the disc, the Mini makes an awful grinding noise, pauses for a moment, then spits the disc back out. Usually, the disc comes out scratched and it even gouged one once. Sometimes it will play a disc the first time, but when I try to use the same disc at a later time it suddenly refuses to play it. I had it looked at and the guy said I just needed to use one of those cleaning CDs in it. I've used a cleaning CD about five times on it since then and it doesn't help at all. Is there any way to fix this?