There I was, mowing merrily along this morning. I heard a thump (lots of pieces of limbs and debris still in the grass from Hurricane Ivan) down by the 400 deck, and the mowing stopped. Normally, that's a sign of a broken belt, or belt that's jumped off one or more pulleys. I wasn't mowing through/over anything that the tractor doesn't normally eat for breakfast. However, I think this instance is a little more sinister. I noted that tugging on the long belt on top of the deck rotates all the spindles/blades freely, whether or not the PTO lever is in or out. I hate to even look, and I didn't have time because something else came up and I had to drop things and leave, and I'm afraid I'll find something major and expensive. Is there anything that could produce the above symptoms that isn't the end of the world (the end of the world being a damaged gear box, broken PTO spline, or broken U joint???