If it's just beginning to let go and appears clean, I would first see if it will push completely back into place with hand pressure, or by using a spring clamp. If it's able to close completely and neatly, I'd allow it to seperate again, put a thin viscocity cyanoacrylate(superglue) into the seperation, wrap loosely with a small piece of plastic wrap(just to keep the clamp from sticking to the bow), and clamp with a spring clamp.
If after it dries(I'd give it at least several hours just to be safe) and there appears to be any void whatsoever, I'd apply more cyano, allow it to dry, and then sand and seal.
I wouldn't remove the overlay completely unless there was dirt in there, or there were pieces cracked, broken, missing, or it just didn't want to go back into place.
Cyanoacrylate(superglue) comes in different viscocities, thin, regular, thick, gel, etc. and everyone who does any work at all on their bows or arrows should keep some around, IMO. I wouldn't be without at least the thin and thick types. I've used a couple of different brands, but lately I've been using Kwik It brand. It's also sold by Loctite, Hot Stuff and others. Bunches of it for sale on e-bay. I believe most traditional archery supply places like 3Rivers and such sell some too.
The 'thin' version is great for this sort of thing because it will seep into the very end of the crack which goes a long way toward created a good, permanent bond.
