texastrees

I just purchased a Craftsman lawn tractor with a hydrostatic transmission.  I did purchase it from a neighbor that recently moved.  The mower is a little over a year old, but I'm having transmission problems.  It cranks up fine, but when I let go of the clutch, there's no forward or backward movement.  I've used it 3 times before with no problem, and have seen no sign of fluids on my garage floor.  I've made sure the release is not disconnected (for pushing).  Also, I've noticed that I can push the mower even if the release is disengaged or not.  The belt underneath is turning.  Any ideas on my trouble?

Thank you!!
Michelle