I would check your wiring at the ballast and at the mogul socket. The insulation on the wires at the mogul will deteriorate over time. Sounds like the ballast is seeing an overload or something and shutting down.
David at Coralvue is a great guy so contact him as well. I have used CV ballasts for years and love them.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,