45 minutes or more for it to fire isnt right. If that happens again maybe try unplugging the ballast and wait a few minutes and then try firing her up again. I am, by no means, an MH ballast expert. Turning a ballast on and off repeatedly probably isnt good for it. But when i encounter this problem, i have just waited 5-10 minutes before trying to fire it again, and it has been working.
Am i doing damage to the ballast? i really do not know. But i figure if it has a few minutes to cooldown and "reset" itself, there couldnt be that much damage done to it.
I hope someone else chimes in, cause i am shooting in the dark here really.