I ended up sending mine to HTC and it WAS repaired under warranty.

Same thing happened to me. My two year old was sitting in my lap, using the phone for two minutes. When I took the phone back the cover was cracked. He didn't leave my lap, or drop the phone. It was obviously cracked from him squeezing a little too hard when using it in kid mode. This kid can't muster up enough strength to pull apart the plastic tabs on a piece of string cheese, how on earth was he able to crack the lens cover? Answer being it's too big and too thin. I've had iPhones that have been through !@#$ and never did a lens cover crack because it's a 1/4 of the size and made of a durable material. Back to Apple I go.