I was trying to take my 4-wheel drive up the snow-covered mountain to get to my house. When it became clear that I wasn't going to make it in low 4, I got out and winched up to a tree on my property in order to get a boost. (The snow is about 4 inches and fresh) As I'm winching up the grade, the Jeep just died. I have some power, but she won't start. The battery is good, and I've checked the fuses and circuit breakers. What could have happened?