I bought my first mac - a 2.93GHz early-2009 iMac - last year, and up until now it's been an awesome machine! But I've noticed a really disheartening thing recently...this wavy-like effect is visible near the top-right of the screen by the disc drive whenever the mac is displaying a blackish background such as a screensaver. Sometimes, it's even visible when it's off. At one point I thought this was dust, but that didn't make much sense to me. I was reading online that this could be due to overheating..if it is, that sounds like it should be something Apple would cover under warranty, right? Because it sounds like it would be a major repair. Also, it seems that the screen has had a more yellowish-tinge in recent weeks...could this be from overheating? I have felt my mac get excessively warm sometimes, but I would immediately turn it off. Help please! Hopefully others have had this and know what to do!