Sometimes when I turn on headlights, especially hi beams, the engine willl stall momentarily. ('03 Accord). Has anyone had this problem?

Haven't had this problem, but it tells that you have an electrical problem in the starting/charging system someplace. Todays cars are very complex electrically and more than likely, when you turn the lights on the car stalls out due to the sudden heavy electrical demand placed on the system causing it to stall. Is your battery the original one that came with the car? If not, how old is it? Most batteries have a useful life span of 5 to 7 years, then they start to lose the ability to handle increased electrical demands and maintain a complete charge. It could also be a telltale sign that your alternator is beginning to fail or that your drive belt is momentarily slipping when the increased electrical load is applied and it needs to be replaced because it is not keeping the proper tension under heavy load demands.