Possible water damage; works fine, but reboots sporatically...
I came in one night to find my Macbook Pro 13" closed, when I had left it open ajar (about 2-3" gap). Upon opening it, I found smears on the screen, the keyboard protector missing, and water droplets on the keyboard. There was no life. The 60w PSU was plugged in, but no green light at all. I figured sabotage. A cat couldn't have done this, could they? No water was anywhere near the laptop. The keyboard protector was on the ground and damaged. THIS, I knew, the cat had done!
After lots of effort to "dry it out" (hair dryer), I opened up the back and not a single speck of water or moisture was visible anywhere. The PSU (power supply) indicator would glow very dim green and then flicker. The system was not coming to life.
I did notice a bit of dusty gunk in one area towards the back of the logic board. I got some 91% rubbing alcohol and a toothbrush and gave it a bit of cleaning. I then proceeded to do the same all over the logic board and then dried it thoroughly with the hair dryer. Plugged it in and the PSU indicator came to life! Bright green! Fan came on, etc. Then it shut down (lid was closed, so it went back to sleep).
I also removed both RAM SODIMM modules to check/clean them and then reinstalled them. Plugged back in and...
3 beeps, repeating over and over. Hmm.
I unplugged, pulled the RAM, swapped them (bottom module now in top slot), and plugged back in. No more beeping. Put the bottom case back on and all seemed well and good again! Yay!
But now it does something very odd and annoying. It will spontaneously reboot at least twice! Usually shortly (within 30 minutes or so) after I push the power button to wake it up out of hibernation (I configured that mode, so I can shut it down, but not have to set up all my browser tabs again when I wake it up). Then it will usually do it once more (tonight it was maybe another 45-60 minutes later). Even idle (I'm not even at the computer). The only things open are Firefox, Safari, and TextEdit. No more than about 5 or 6 tabs open in either browser.
Some keys also repeat sporadically, but that could be the damaged keyboard protector "sticking". Not 100% certain. Have the protector off right now and I think it may still be doing it.
It hasn't rebooted since (tonight). Not sure if it will. Hope it won't. :-D
NOTE: I'm running MacOS X 10.7 (Lion). Why? I absolutely HATE the flat, boring UI of the latest versions. What's the latest version that DOESN'T have that?