Small Engines (Lawn Mowers, etc.): Scotts S2046 Drive belt problem, scotts s2046, good shape

Question
My Brother-in-law was helping out moving some brush when while driving the drive belt came off. No Biggie I thought, pulled out the manual looked at proper threading and fixed. As soon as we start the engine the belt jumped off again. Ok I thought Belt was old and looked stretched so purchased a new belt and replaced. Same thing is happening as soon as engine is started the belt jumps off the pulleys, Checked all pulleys all look in good shape, Is there something I am missing? What is happening and what should i look at next. Thanks for your help.

Answer
I tell customers every day that when they have a belt problem it is never the belt.
I'm guessing the source of your problem is a broken or missing belt guide, or a case of hidden crap in pulley.
Rotate every pulley all the way around and check for garbage in the sheaves. Look at the parts breakdown and make sure you have every belt guide and that they are adjusted properly.
Check out these links to see if you are missing a belt guide.
http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H...

http://jdpc.deere.com/jdpc/servlet/com.deere.u90490.partscatalog.view.servlets.H...