1995 Buick Century

I have a 95 Buick Century V6 with 100,000 miles. It has just recently presented with these problems. The headlights do not work, my powerlocks don't work, my dash lights don't work (except for my clock and radio and my clock and radio presets rest every time the car is turned off), my anti-lock brake warning light is on, and my dome light is out. I have had fuel injector problems recently but those have been fixed for now. A mechanic looked under the dash and the lights and everything started working for him he wasn't sure what he had done and he couln't reproduce the problem. This lasted for a couple days and now all those problems are back. What do you guys think? Thanks.