I just got home early from my weekend riding trip because my 07 YZ450 broke down. I was riding down a dirt road in 4 th gear, doing about 45 mph when my bike suddenly popped out of gear and I heard a whining sound coming from the engine. When I gave it gas it just reved up and went no where. I turned the bike off and tried shifting it into neutral. I got it back in to first and decided I better get back to camp. I got about 20 feet and the bike locked up, engine died, and I slid for about 10 feet. At this point the bike would not shift up or down. It is stuck in gear. Even when I pull in the clutch, I cannot move the bike without dragging the rear tire. The weird thing is I can start the bike with the clutch in, and it runs fine, no whining sound, but when I let the clutch out it just dies. I have had a lot of bikes and I have never had a problem like this. I am frustrated because I have only had this for a little over a year and I always maintain my bikes and never abuse them. Any help on this matter would be greatly appreciated. I have no idea what is wrong or how much it is going to cost to get fixed. Thanks.