Why is my MacBook Pro not charging?

"Find yourself an Apple Store, show them the issue, they may replace the battery right there if it's in warranty and the battery is easily removed (unlike the newest line of MacBook Pros). I've had them swap out my battery on an out of warranty machine too.

I believe the basic test for you is:

Apple Menu >> About this Mac
Click More Info
Find the section for power/battery
If the age of the battery is less than a year and the charge count (cycles) is less than 300, they have often replaced the battery on your reported symptom.

Of course, Apple has a fancy battery testing tool that they will reboot your computer into once you're there in person, so I implore you to find an Apple Store, an Apple Certified tech who won't charge you for warranty repair, or contact Apple Directly about the issue.

For more info on what counts as a ""cycle"" read this http://www.apple.com/batteries/

Similar issue discussed on Apple's Discussion forums: http://discussions.apple.com/thread.jspa?threadID=1296373"

I had the same problem some days ago.I did not know what to do but since i was travelling i just packed everything and went away.Some hours later i plugged the cable again and it started charging again as usual.It happened to me a second time but this time it started to charge sooner than the first time.In both occacion that happened when i let run the battery below 2%.

"I had the same problem. I didn't want to go and replace the charger unless absolutely necessary. I inspected the cables and didn't notice any damage on any part of the cable or charger. As a final measure I decided to try and clean the contacts and the magsafe power socket. This did the trick!

It appears that the charging socket has a low tolerance for dirt, grime or debris. I took a cotton tip and dipped it in a solvent such as mentholated spirits and wiped the gold-plated contacts of both the plug and socket. Make sure there's no dirt there stopping the plug fitting as if it were brand new.

Once its clean it should work as new! Anyway worked for me and I didn't have to fork out for a new charger :)"

The MacBook likely believes there's a power source plugged in because there could still be electricity passing through that line that the MacBook can detect, although the power source itself may not be functioning correctly (sending a powerful enough current) and charging the battery.