1999 Jeep Grand Cherokee starts but wont stay running.

I have a 1999 Jeep Grand Cherokee that has 162000 miles on it and this is the first time that it has happend. But I had misplaced my keys and I had tryed jiggalying it with another key didnt work and then I opened up steering colom and messed around in there still nothing. So the next day I had found my keys and I go and try to start the jeep and it starts but it dies after a few seconds of running. So I went and disconected the + cable to reset the computer wait a few min and reconnect the terminal and go and try to start it again. Again same problem. There is a light that flashes that has a sign of a key and a line through it. I dont know wht it could be. Could I have messed up the ignition switch? Please help me.