It's not an uncommon problem, and it's covered by your warranty. So in the first instance, contact microsoft and they should arrange for a replacement console.
If you have no warranty, there are several sites that offer guides on how to repair the problem for free, but it requires taking your console apart and making a modification, so obviously don't do this unless you are confident in what you're doing and don't mind potentially breaking it beyond repair. Possibly find someone who can help you that knows what to do.
