Macbook pro charger cable.. broken!

I have only just realized that my macbook pro's charger has broken at the neck, right under the plastic part that attaches to the computer. The wire inside has frayed and the coated layer of the wire seems to have melted.
I have only had my macbook pro for 5 months and am very disappointed this has happened already. Has this happened to anybody else? But more importantly, will Apple replace my charger free of charge under warranty?
Thanks guys.