Since this is a pretty common issue among macs, I thought I should share some information on the subject. If your magsafe power adapter is dying/working intermittently/dead, check this Apple Support page article before dropping $80 on a new magsafe. Take it into an apple store for a free replacement whether you’re in or out-of-warranty.

I had some problems doing this at the UTC Apple store with the ‘genius’/supervisor (which I documented on yelp), but it was resolved immediately once I called apple. Apple sent me the newer style model too.