Hello all....I'm having a problem with my Snapper rear engine rider mower. It was working fine two days ago when I mowed my lawn with it, but today I went out to get on it to mow a little more and the gear shifter won't let me go to reverse or forward, like it's locked up. Any ideas? I'm not real familiar with Snapper mowers as yet, although I've had this one for about 3 years, I've had to do very little work on it. Please help!