Daybreakers. Vampires have taken over civilization and are the world's biggest population, but with humans facing extinction, they are facing starvation. Brilliant idea, cheesy B-movie execution.
Man, I've been trying to figure out the name of this film, but I watched it when I was still in high school and only had faint memories of it. Finally cracked the search by looking up "zombie vampire movie sunlight disintegration."
Reading over the plot makes it sound like it has the potential to be a thought provoking film.