Godaddy - Error 500

I'm using Atahualpa 3.6 and WP 3.0.4 with Godaddy hosting. The site has worked fine up until today with no changes and now I get the 500 Internal Server Error. I can access the backend fine but can't figure out why it's not working now. Godaddy says it's a theme issue but I dont' buy that since it's worked in the past and I have other sites that are working fine as well. The only thing is that other themes do work. I also turned off all plugins to no avail. Any thoughts? Thanks.