Just yesterday I plugged my Macbook Pro up as usual and a message in the top right-hand corner informed that it was "not charging." However, the computer was only at 4% battery when I plugged it in. This charge was maintained despite the insistence that the computer was not charging. Moreover, over several hours, the charge reached 22%. The magsafe charger is not the problem as my roommates have used all of the ones I have used and they work fine with their macs. Any thoughts as to what the problem might be?