Ok so I was too hasty saying it was the bulb. After running for about an hour, the issue started up again. Then after the first day I would only get like 10-15 min after the bulb fires and then the problem is back. Not sure why it takes this bulb a few minutes, but whatever...
The real update is that I got my new Lumatek ballast Monday. Installed it that night and been running since Tue morning with no issues at all. I'm still using the same mogul/reflector/bulb setup that I had the issue with, so it's definitely the old ballast (especially since it did it with two different bulbs, one of which was the stock bulb).
Fucking cheap ballasts. Won't make that mistake again.