This morning i started a small project, fixing some rust & rust holes..

I sanded the rust areas and also all the paint for about 2-3" out
past the rust areas. I then applied the body repair filler and got
it all sanded, and decided i'd just go ahead and paint it today
since i was doing all this anyways. So i drove to the auto parts
store.. Parked and ran inside, got the stuff i needed. When I
came back, I got in my car and went to turn on my car like usual..
Well this is where the problem started..

I pushed in the clutch all the way, turned the key to the start
position and nothing happens.. I look at the dash gauges to see
if my battery went dead.. All of the sudden I noticed all the
gauges start to turn off, they all drop down to like the off position.
So i try my headlights.. not working.. Then my radio, A/C, etc.
Nothing worked! I was going crazy, so I ran inside, bought a new
battery and put it in, made sure that the wires were back on nice
and tight.. Still didn't work. So I called AAA, got the bird towed to
my mechanic, he was gone for the day, so I had them tow it to
my house. I pushed it up and put it in it's spot.. I then started
checking fuses naturally.. Electrical - Fuses.. Of course, this must
be the problem! - Wrong! I changed out all the fuses, even
though not even one was bad. Still nothing.. I looked at the cig
lighter outlet to see if maybe something dropped in there and
shorted it - nadda. So then I double-checked the battery wires..
Perfect, all tightened down. So now NOTHING in my
dashboard works, absoultely nothing. This includes:
-Gauges
-Radio
-A/C
-Headlights
-Wipers

It seems, the only things working are the hatch and dome light..
Any idea's out there? I checked out the
Haynes Manual - 1982-1992 Pontiac Firebird (ALL MODELS)
for something about electrical, troubleshooting, all that.. Nothing!
So I'm hoping somebody out there has had this problem and can
tell me exactly what must be done.. Please help!

**Update**
When i flip the headlight switch on, the front,side, and rear lights
come on, but the headlights to not flip-up. I was thinking - could
this all be a problem with the computer?