"Dead On Arrival". It's police and medical jargon for someone who has been taken to hospital but dies en route. Used in the theme song metaphorically to suggest the love life in question is somewhat stagnant.
DOA - Dead on Arrival - Hospital speak for someone who didn't make it in time. So a DOA Lovelife would be no lovelife or a pathetic love life whcih seems in keeping with the rest of the lyrics.
-AT