After an hour of mowing, my mower won't go forward or backwards. What do I do?

Your main drive belt may be slipping as it heats up. To check this ask a friend to observe the belt when you start cold, this way they know how it should look. Then have them observe the same belt when you can't move forward. If the belt is slipping try tightening the tensioner pulley. The tensioner is the pulley that moved back and forth when you hit the clutch/brake. If all your adjustment is used up it is probably time for a new belt. By the way, keep the blades DISENGAGED for the safety of your bud.