It's so funny you should mention that. Mine has been doing the same thing.
Interestingly, it is NOT hungry grumbles for me. Simply gurgly noises. It isn't heartburn or lactose intolerance, either, which is described in the FAQ's. Just a sort of bubbling grumbling.
I decided that my tummy is PO'd because it misses its yummy treats, and I've decided to ignore it. It works with my kids when they are having a tantrum, so why not my belly???
Still, if there are any words of wisdom out there I'd love to hear it too!