Craftsman stuck in high gear!!!

Hi there,

I have a Craftsman LT1000 model #917-272072. The problem started a little bit back, I was having trouble shifting between gears especially getting it out of and into first gear. Well the other day I was mowing and it got stuck in reverse and I gave the shifter a bit of force and it pop out of reverse and went all the way into high gear (6). Unfortanutely again getting completely stuck in gear. So I finished mowing my yard in high gear with alot of brake use. After I finished I parked it and tried to get it out of high gear to no avail. I eventually tried to use force as I did when it was stuck in reverse. I only ended up breaking the mounting bracket for the shifter handle. What would be causing the gears to be getting stuck like this? This is my first riding lawn mower and dont know alot about the workings of the transaxles in these. FYI the mower is in great shape very clean I pressure wash on a frequent basis to keep from any clipping from building up on the underside of the mower. Thanks in advance for your help. All suggestions appreciated!!!