Im going with the Main Relay. do you have an alarm with a kill switch. i had an old alarm on my prelude that wasnt working when i bought the car, mysteriously one day my car had the same symptoms as yours, tried everything without spending any money, then a friend told me about his experience, needless to say i yanked the alarm wiring and voila, it started.

maybe even the clutch switch??? i have heard those give the same symptoms you are having