Got a weird issue here! I've been given a 2008 macbook which claimed to have a laggy trackpad. They thought it was overheating so I applied some new (and much needed) themal compound and manually maxed out the fans but temps were in the 40s, so no issue there. Initially the trackpad was lagging behind quite badly but the longer it was left running, the display started to freeze, fade slowly to a grey tint (with the desktop still visible behind) and any trackpad movements wouldn't register until the display came back to normal a few seconds later. This cycle kept going, but the fading took longer and the icons had faint inverted colours after about 20 minutes. I have tried a SMC and PRAM reset but with no result. It seems like a thermal issues as it gets worse the longer it's left on and rebooting doesn't help, but I can't figure it out! Help!