I also discovered after going gluten-free that I can't eat corn, either Some corn tortillas (can't remember the brand) that were labeled gluten-free made me sick. I also tried gluten-free corn pasta and tortilla chips, but alas, I can't eat them without having symptoms. So, it could be corn or some other ingredient that you can't tolerate. However, I also...
I second the wholly guacomole recommendation. It's almost as good as fresh, and comes in individual packs that are easy to take to work. It's also labeled gluten free.