Why did my TV signal get weak and the networks change channels?

I recently got a new big screen TV. Shortly after I got it home, we had a bad storm and the power went out. The next morning, when we turned it on, it could only find a few of the channels we had before. Some of them can be found by typing in the channel numbers, but most of the channels are different now, the local channels are static and the provider says it's something in the house, not in the line or service.