Internal Microphone is not working MacPro

My internal microphone recently began to stop working during a coversation while using Skype. I have tried many things such as checking my sound perferences to adjust volume of mic and restarting my computer, but nothing seems to work. Something restarting brings in back, but not always. Is there anything else I can do?

I purchased my MacPro just last year and it's still under warrently, but I'm currently living out of the country in Japan. If need be will my local Apple store repair it free of charge?

I look forward to a repsonse.

Best,

-K