I would measure the voltage at the light..each one, usually with a low voltage, or poor connection you would notice a difference in brightness, or a dimming when other loads are put on that circuit.
If the lights are burning out, it may be a bad connection, or improper bulb for the socket, both of these are inter-related. If the fuse blew, I would go with improper bulb or shorting out the socket with improper insertion: dead short.
Hope that give you fodder for investigation, and not just a headache from reading it..