No electric except engine/starter/headlights

My 1993 Infiniti G20 w/ 170,000 miles was running fine. It sat for 2 weeks January 2004 in Massachusetts winter while I was on vacation. Next time I tried to start it there was absolutely no electric (no clock, gauge, juice to starter, nothing). Jump started it and it started, but clock/gauges etc blinked on/off repeatedly. I drove it to a shop - it ran rough.

After chain run auto store put in a battery and checked it, only the engine would run and the headlights come on. The battery is not charging now, but I think that is just the alternator not working. Not sure if it is some master fuse or the computer brain or something else. Thoughts?

Thanks.

Still got it, but need some leads as to possible problems.