Originally Posted by TheSoCalledJohn
Sounds like you're having the same problem I was having. When I turned the key to the accessory position (first click), the radio and lights all came on fine. When I went to start the car, everything went black.
Turns out it was a bad connection on the negative battery terminal (could happen just as easy on the positive side). Cleaning the battery post and the clamp worked for a little while, but eventually I had to change the clamp.
I think that's exactly what it was. I figured it out when I jumped it and noticed that the battery wasn't charging. That was both a relief and an easy fix!