Aging Macbook Problems - sound going out/shutting down randomly when unplugged

Question

My macbook is from July/Aug 2007, so it's not quite 5 years old. One of the problems I have been experiencing is when I have a full charge and unplug it, usually around 80% or so, it'll just completely shut down. Doesn't matter if I'm running one thing or multiple things. I've had my current battery for almost two years now. My cycle count is 150. The battery isn't bloated or anything. (My last one started to, which is why I got the new one.) Since the cycle count is so few, it should still be under warranty, I believe, if that's the probable cause of the shutdowns.
I have also been getting kernel panics maybe once every other week or so for a little bit now. Usually it happens when I'm watching video online and it'll freeze and the message pops up. Only just researched more about it and found this: http://support.apple.com/kb/TS3742?viewlocale=en_US&locale=en_US
Going to do some troubleshooting and see if I can figure that one out. Any chance it's related to the random shutdowns when I'm not plugged in?
The last thing I've noticed is also when I'm watching video online, sometimes my sound will go out and will be replaced with an intermittent crackling sound. I read a few forums and found that if I put headphones in and out of the jack, it'll fix the sound back to normal. This sound problem doesn't happen very frequently, but a lot of the time when it does, it'll happen a couple of times in one sitting. So far, I've never noticed it happening when I'm using Itunes or watching a DVD, only stuff online like youtube or when watching my slingbox, etc.
Any helpful comments are greatly appreciated!

Answer 1

Ummm, nope. All due respects, this problem cropped up suddenly, at about the same time, for multiple users, on different laptop types. Probability of all this happening at once due to simultaneous hardware failures is much lower than if it was caused by say a software update not playing well with something (a piece of 3rd party software, etc). I'm having the same exact problem, I have put a new battery in, same thing happens.
This is similar to 3 or so years ago when widgets were first introduced, laptop battey lifes dropped to about 1/3 and the machines heated up. General consensus was it must be hardware, well no it was software, and a software fix took care of it. I'm hoping someone figures this out soon...
Thanks