I had The same problem with my upper chest bone somethimes it cracks and pops to when i caugh our take a really deep breath and i was wonderning if that was normal our will it go away by it self threw time.
No. It sounds to me as if there's a joint stability issue. I know that in my own practice, the popping/cracking sounds patients experience dissipate over time as the spine is restored to a normal position. Consider calling a local chiropractor and ask him for an examination.
Warm wishes,
AT