It could be any number of things including the AC Adapter, the battery, the charging port, and/or the motherboard.
Sometimes it's just that the tiny pin-like contact in the center of the AC Adapter plug is not making good contact inside computer's charging port. That tiny pin is how the laptop reads the Adapter's digital identity to ensure it's genuine.
Thanks for the fast reply. Normally I'd just assume that was the case; that it was a minor hardware issue, and that there's an issue with the charging port. It just struck me as odd that each time it happens, re-seating the battery fixes it for two weeks (almost to the day) before it happens again. Any suggestions for possible fixes? I'm thinking about reformatting my hard drive and reinstalling all of the drivers in case it's a software issue. Also considering replacing the battery (hopefully I can find a place to get a replacement that I can return if it doesn't fix it...). Either way, I'd like to exhaust my options before I drop almost $500 on a repair that might not be necessary.
Issue persists for me as well; for what it's worth, I've been able to fix it whenever it rears its ugly head. All I have to do is unplug the battery and re-seat it every two weeks or so, and I'm good. An inconvenience that is sure as hell not worth Dell's (ridiculous) $430 non-refundable charge to send in to fix. I just won't buy a Dell product next time, methinks. Tired of all the heartache over their shoddy products. If it breaks down on me, I can always go back to using my Alienware M17 that I got back in 2008, before the buyout. The one that still works fine after 6 years, while my <1 year Dell one is going nuts.
Just in case it helps, I think I found the problem. It's been 3 weeks since I adjusted to compensate, and the issue hasn't come back yet. If you use the 'power saver' option on the computer (the one that uses up battery to conserve battery life when it's plugged in all the time), try turning that off and see if it helps.