My Mac: Early 2008 15" MBP, 2.4 GHz Core 2 Duo, 2GB RAM, NVIDIA GeForce 8600M GT, running Lion. I was finding my Mac running slower than I'd like, so I ordered this RAM from Crucial. It's guaranteed compatible with my model of MBP. After installing it, my Mac felt brand new. It worked better than ever. 10 days later, I woke up one morning to wake my Mac, but it wouldn't turn on, plus it was very hot (no fans were on). I unplugged it and removed the battery, waited 10 minutes, and hooked everything back up. It started up normally, but the fans kicked in right away, so I'm assuming it was very hot inside. It worked normally after that. 7 hours later, when I went to wake my Mac, it wouldn't turn on. I removed the battery again like before, but this time it would turn on for about 1-2 seconds, then shut off imediately, just like in this thread. I switched to my original RAM, but the problem remained. A few days later, when trying to power it on, the sleep indicator light would turn on and off in less than a second. I took it to an Apple Store, where they said the logic board had failed. They replaced it. All seemed well, though the hard drive sounded a little different when starting up. When I got back home, I reinstalled the new RAM. Everything was running nice, but a few of my Mac App Store applications were not opening, even when I checked that my account was authorized on this computer. I decided to restart my Mac to see if that would fix the issue. It shut down normally, but when it booted up, it got as far as the Apple logo, then it shut down. I switched back to the original RAM, but the problem remained. I took it into the Apple Store again. This time, they said it was the hard drive that failed. They said they'd try reinstalling Lion, and, if that didn't work, replace the hard drive. This brings us to present time. The hard drive was replaced, and it runs like new. I haven't seen my fans go more than 2010 RPM, all the sounds it makes sound like they used to, and my Mac feels less sluggish, even with 2GB of RAM (though it doesn't seem as fast as it did with 4GB of RAM). Here's my question: could it have been the 4GB of RAM that I ordered from Crucial that caused the two problems? Or is it just a coincidence? I don't want to install the RAM if it's going to damage my computer, but I also don't want the RAM to go to waste (plus I'd love to have 4GB of RAM again, as it really boosted my productivity).