Bill,
I build quite a few board bows, and have had similar things happen. I now back all my board bows with rawhide. It makes for a VERY durable bow and avoids any problems with grain run outs or the like. That way I don't have to spend quite so much time going through the lumber racks searching for the "perfect" piece. If the bow you mentioned hasn't formed a hinge at the bad spot you could still back it and see how it goes.
I sometimes get my rawhide from trad. archery suppliers, but recently have been getting good stuff for a great price from a local saddle maker (they use it to wrap the horns on ropping saddles). It is of a good consistant thickness and just right in width.
I size the back of the bow with titebond II and let it dry over night (an even coat is best). Next day I soak the rawhide till pliable, recoat the back of the bow with glue and apply the rawhide after "squeegeing" between my fingers to remove excess water. Get all the bubbles out and smoothed down, then I wrap the whole thing up in vetwrap and let it dry over night. I use a paint stir stick (free from Lowes, HD, etc) with sand paper stapled to it to take off the excess (a lot of books say use a rasp, but I tend to take off as much wood as rawhide that way) and round the edges. Finish up the bow as you like.
Good Luck,
OkKeith