Are you sure they are physicaly on two different circuits?
I just want to make sure, because some people call receptacles and lighting two different circuits even though they are one.
I just want to make sure that we all are on the same page.
If you can get a hold of a meter that has recording capability. (Max, Min, Average) hook it up at the suspect circuit, turn on a resistive load (hair dryer) inside the house and see the voltage reading on the meter. If you have a large voltage drop at the output of breaker then move the meter to the bus bar, if you still have large voltage drop then call POCO.
Now, if you don't have large voltage drop at the breaker but have flickering lights inside the house (with your hair dryer on) then the problem is inside.
I am suggesting a hair dryer because it is large load and you want to put some strain on that circuit in order to create loose connection or flickering effect on that circuit.
