I tried stopping the array and stuff, which got stuck, and ended up rebooting a few times. I also uninstalled the Network Statistics app, or something like that, which I'd installed shortly prior to this happening. I also disabled the Recycle Bin plugin. I'm doubtful either of those things was related, but who knows?
I, too, am having pretty much this exact issue as of this evening. Shares disappeared. Data is still on disks. The disks themselves are shared, apparently. New shares immediate deleted...