I lose power for a few hours then gain it back. My circuit breaker is not tripping, and I tried to replace the breaker but still same issue. I also checked the gfci outlets and re-set them but still same problem. What can be causing this?

Which breaker is the breaker?

Sounds like you have a problem with the main breaker. This is not something a diy should be messing with. Please call an electrician.

I have two boxes, one that piggy backs off the other. In one box, all the breakers on the right side lose power. In the other box, it is a scattered few. Any idea how much it would cost to have an electrician replace the main breaker?

Probably not much more than a service call plus the price of the breaker.

Have you contacted the power company?

This sounds to like you are intermittently losing one leg of the power to your home.

This can be caused by a bad meter base, or a fraying cable that is unable to make a complete connection. From the meter back to the transformer belongs to the power company. Call them, the worst they could tell you is that it is not their problem.

Power company said everything is connected correct on the pole but they are not allowed to stand on my roof to check the connection to my house. So far today, I have not lost power... odd that everything is OK after the power company checked their poles.