Eureka! Man, I feel like the f-ing master of the universe right now. I got home and tried userpay's suggestion, switching the tags around, but no dice. Thinking I might have changed something in the other raws while trying to alter reactions to create shell, I copied the mtn goat raw over to my backup, but it still crashed. It even crashed when I tried copying in the dwarven pig info from here:
http://www.bay12games.com/forum/index.php?topic=53533.0 into the mountain goat raw. I thought since it has shells it would work, and maybe the crash was something to do with how the strings were added in mountain goat. But no go.
I realized it only crashed when I went to look inside the butcher's shop to see if the shell had been created, something that I always did. So, I tried using a new butcher's shop. I deconstructed the original one and built another near by. Worked like a charm.
So, the two lessons to take from this:
1. It's not that important where you put the strings for shells, since the dwarven pig had them in really strange places, it's not to do with that.
2. Use a new building if you're changing the raws. Who knows why, but it didn't like showing me what it held. I wonder if it's because I'd slaughtered goats in there before and it still had their products inside. Maybe it freaked out because it couldn't locate the shells that never existed.
PS: thought you might like to see what he made. There isn't even any shell visible! WTF!? Value is ~65k.