Sort of a DME issue
 

I jumped my 911 off my 1984 944 and the next time i drove my 944 it was running perfectly up until about 10 minutes into the drive when i noticed the radio cut out, the battery light came on for a second before the entire car shut off while driving.

Sounds like DME, but I'm curious why the radio would be reset and the entire electrical system would shut down from just the DME.

Is that normal?

The radio has nothing to do with the DME... odds are, it's a problem with the battery connections or ground cable or something. Hopefully, will be obvious when you dig into it. The battery light comes on when the alternator is no longer charging the battery. So maybe it could be a problem with the alternator ground or power wiring.

That's Where i was getting confused. I couldn't work out the radio part. IT was as though i disconnected the battery for a second then re attached it.

Grounds look good, but I'll get to cleaning. it started running right back up with no issues afterwards.

Hopefully just a ground as you stated. But still odd for the car to cut out like that.

ignition switch.

While a connector at the battery may look OK, it is more often bad at the other end. And corrosion inside the cable is hidden until you actually open up the insulation.

http://i42.photobucket.com/albums/e3...F.jpg~original
http://i42.photobucket.com/albums/e3...F.jpg~original

The positive cable can have similar damage and corrosion as well. The "battery" light on the dash doesn't actually indicate anything about the battery, except that it's saying "battery's not being charged". This is a sign that the alternator's VRM is bad or the cable between alternator and battery. The light is technically called a "charge lamp".

how well is the alternator charging ?
You might have damaged the rectifier when jump starting so that your alternator isn't keeping up with your battery loading