I have had some transient problems with the circuits in my house. About half of my circuits to several locations have a tendency to cause lights in the affected circuits (yes multiple circuits) to go out, but not trip breakers. It happens seemingly at random and affects washer, dryer, central air kitchen appliances, but not refrigerator. What is weird is that turning on the ceramic cook top almost always sends it into 'remission'. I spent over $350 for a licensed electrician to troubleshoot my wiring. He told me that I had no earth or cold water grounding. I grounded the ground/neutral bar in the panel to a copper clad rod outside the house 8 feet deep in sand and to a cold water copper line. I tightened the ground feeder to the main breaker. it was a bit loose. Can't tell about the other two feeder wires because I'm not suicidal with metal hex sockets. The transients are STILL happening. I'll call the electrician again because he should have checked those lugs. and the electric company says their end is all hunky dory. Is there anything else to check? I am not an electrician.
(Edit)I was able to observe the panel during a transient. Some rock wool insulation had fallen on the main 200 amp breaker. There IS arcing on the buss bar behind it. Ya'll were were right and i will likely have to replace the whole darned thing. Found reference here to my problem. http://www.diychatroom.com/f18/200-amp-main-throw-arcing-168804/ Thanks to all.