Same thing happened to me - my QC2 broke in the same place (whilst on the plane and I had to use some tape to hold it together). I believe it is a common problem. I too had bought them in the US.

At the same time, the ear pad had started to disintegrate so they were due for the dustbin.

On another trip to the US last year, I went into a Bose store to enquire. Despite being 10 years old, they offered to take them back and give me the new QC3 model for $99 I think.