1995 Pontiac Bonneville Wiring Problem

I am working on 1995 Pontiac Bonneville for a friend. She was on the highway and said the car just died and wont start, so I had her tow it over to my garage. After the truck dropped it, it started right up and died about a minute later. I checked and it was getting spark so I figured fuel pump. After pushing it in my garage I also noticed that the power windows, locks and seat were not working. I called and asked her if they were working prior to the car breaking down and she said yes. So now I am thinking an electrical problem. Battery is brand new by the way the car cranks strong. So I started by checking the basics, fuses are all fine both under the hood and dash. The relays all seem to be fine. I also noticed the the indicator light on the rear defog button is on even with key off and when you press the button with the key on it shuts the dome lights off. All very strange. Now I have all the wiring from under the dash to about the sides of both front seats pulled up and there does not seem to be any obvious frayed wires or cross shorts. I was playing around with the fuse and relay center when suddenly everything started working for a short moment but then stopped. I was hoping I had it traced to that area but have not had anymore success. Is there possibly a computer that controls those things that I don't know about? I'm a pretty experienced mechanic but this problem has me at wits end. I have been working on this car for 2 weeks. Please help and thanks so much!