You don't need to buy extended AppleCare. You are still under the one year warranty. You should call support or if you are close to an Apple Store or Authorized Repair Center make an appointment. The 90 days phone support is for:
http://www.apple.com/support/complimentary/
Complimentary hardware support provides telephone support for basic setup, installation, assembly, and connectivity. See the support-related materials included with your Apple product for more information.
Complimentary software support provides telephone support for installation, launch, or reinstallation (not including data recovery) when your hardware configuration meets the minimum system requirements for the software. See the support-related materials included with your Apple product for more information.
It won't cost you anything to call support about a warranty issue. Here's the worldwide support contact list:
http://support.apple.com/kb/HE57