Electrical/Transmission grind problems connected?

[rooger]

Yesterday I started my 2003 Mustang V6 auto transmission after it had been parked for a few weeks. (None of the forthcoming problems existed the last time the car was parked.) First, I noticed the air bag light was on. As I continued to drive, I noticed the following were not working: directional signals, a/c, power windows, cruise control, windshield wipers, radio. Some circuits were working such as power door locks and horn. No other indicators lights were illuminated. When I reached my destination, I attempted to put the transmission in Park and I heard a loud grinding noise. I then tried to back up but got the same loud noise. I shut the car off for awhile. When I restarted it, the air bag light was off, all the problem electrical circuits were working again and I could shift the transmission through all positions without any noise or difficulty.
My initial thoughts were that the electrical and transmission problems were somehow related to each other. Maybe an on-board computer or PCM needed to reset which was causing a transmission servo or solenoid to incorrectly activate the "Park" components (sprocket/pawl) in the transmission. Hence the grinding noise. I also thought a poor ground circuit could be the cause. I drove the car today without any problem. Any theories, folks?