Does this look structural?
I don't believe it to be a structural issue but a bad tape joint as @Tester101 mentioned in his comment. There's a slight possibility that this is a byproduct of a small roof leak too, tho not likely in a 5 year old home. Also, as @Tester101 mentioned, it's difficult to say without being able to physically inspect the structure ourselves.

Bubbles in taped joints are caused by not having enough mud behind the joint tape. If I were to fix this, I'd cut out most of that seam and redo it.