I have a Late 2008 MBP 15". Last year the power started behaving oddly, the power icon in Mac OS X would say "plugged in, not charging" when the cord was plugged in. Sometimes the cord's light wouldn't be lit, while plugged in, or it would turn green when it was supposed to be orange.
I could get it to charge properly by wiggling the magsafe connector laterally along the surface of the magnet. It would slowly act up worse and worse over time, it would take more and more tweaking to get it to charge the battery. I finally ordered a new DC-In board and replaced it, and the Magsafe connector worked fine for a while again. It's now repeating the same behavior and getting worse.
What could cause this part to go bad in the same way as before? I don't plug/unplug my cord very often, so it's not wear and tear. I don't hear a lot of other people with the same problem, so I'm kind of annoyed with this issue. Thoughts?