I had the exact same problem. I freaked out. No matter what I set my limit at, it always stopped at $50. And not just $50 for each campaign but for all of them total. Drove me nuts. I finally contacted "G" and asked what the hell. They replied that all new accounts are set at $50 daily limits by default and that in a ew days I could set my limit manually, and sure as hell, 2 days later, I was able to set my daily limits.
Just got to wait it out. But it sounds like you are good to go now!