Electrical Glitch...uh-oh

[Bill]

Just a LITTLE electrical problem:
Two nights ago, while completing the last leg of a 275 evening run, my lights suddenly started to flicker BRIGHTER than bright and my instrument lights were also bright enough to read by.
The engine als started to cut out., but after a couple of minutes, this stopped and everthing went to "normal" not to return...yet.
The battery reads 12.5+ and the alternator is puttting out 12.5+, but the 'generator' light on the tach pod does not come on when the key is first turned on, but glows dimly at idle and while running.

Any ideas on what is going on??? '78 Spider, by the way.
Thanks to all