This is normal -- the problem is that most broadcasters assume the TV is overscanning, and sometimes they don't care about having the picture go to the edges, or there's additional information transmitted in that area (if it was at the top of the screen, that's often the closed caption information).

Best thing to do is to use a different picture size -- I don't know what the B-series renamed everything to, but on the old TV it was called "16:9".