This one is the older cone drive system. Went out this evening and cut the back yard, everything working just fine. Shut it off to grab a bite of lunch, started it up pushed the handles forward and now the mower won't move either forwards or backwards. Blades are still engaging. Parking brake not engaged. Any advice on what to look for would be greatly appreciated. Mower I think is in the neighborhood of being 17 yrs old or more this is not the original cone drive, I put about 2 grand in that about 10 years ago.