Burning stomach pain after eating raw foods?

Recently I went to a raw potluck, and the food was wonderful. However, about an hour after eating, I started getting a really bad, burning stomach ache. This happened once before when I went to a raw food restaurant. I've made raw food at home and this has never happened.

I'd really like to eat more raw but not if this keeps happening. Anyone deal with this or something similar? It really doesn't feel like detox...it feels more like an ulcer!