Cory, install the belt, lower the deck then look at it from the side. Does the belt line up with the center pulley or does the pulley appear to be nose down? If it appears to be nose down, check the lift rock-shaft where the mower sub-frame fork sets and see if there is a worn spot on the rock shaft and/or on the sub-frame fork. Also, check the front lift points on the sub-frame where they fit into the clevis on the front of the mower deck, are they worn? I had the same thrown belt a problem and mine was caused by wear in the points that I mentioned. I had a good friend do a little welding for me that took care of the problem, no more thrown belts.