Bought my nieces a Kindle fire each last Christmas, from Amazon, they both are now not charging up any more? when plugged in the light on the unit comes on to say it's charging but it never does.

Could understand one failing but find it strange that both would develop the same problem at the same time, googling the problem proved inconclusive for me so thought i would ask on here before getting on to Amazon.

So has anyone ever had this problem?