400Watt Electronic Ballast Cutoff

Ive got a 400 watt electronic ballast in my pj.

It runs for about 2 hours then cuts off.

I have 2 80mm fans blowing into the lightbox and 2 80mm fans blowing out...

First I had the ballast right next to the light, and had the cutoff problem...

Then I moved the ballast away from the light, but it is also not near the fans.... still same problem.

Is it more important to cool the light... or the ballast?