Today I went out to my car (2000 Deville) and started it. I was about to shift into reverse and drive off when I noticed the gauge cluster was not illuminated. I tried sliding the twilight switch and pressing some of the buttons that control the message panel to get it to light up. When that did not work I turned the car off and tried restarting. The gauges immediately lit up but now the car wont start. Also the radio will not power on at all and the temperature readout on the climate control is showing dashes even after the car has been sitting for a few hours. When you turn the key you can hear the fuel pump engaging and the ignition relay "clicking".
So far I have tested the battery and eliminated that as a cause. Checked all the fuses and they look good.
Any advice on what I should check next would be appreciated