lights out

About 8 years ago I installed some track lights on 2 sides of our ceiling. The
lights are about half way up both sides of our 20 foot A frame ceiling. I know
when I installed them I installed a breaker for each set of lights. Each side
has 3 lengths of 3 65 watt lights so it would be 585 watts on each side.
Gradually the lights went out on one side. About 2 years ago, I tried to
replace the burned out lights and none of the replacements worked. The last of
the the lights went out about a month ago. I was in the room and the last 3
went out at the same time. I tried to replace the lights on that side and none
of the replacements worked there either. I know I had breakers that could
handle the wattage on each side. Does anyone know why the replacements won't
work? Does anyone know what may have gone wrong and what to do about it?

Thanks
GB