I've had an electrician over twice -- he says he has checked/replaced/fixed absolutely everything. I've had the power company over twice and they can find no issues on their end. This morning, some of my power was out completely (some things were still working) -- on all floors. I am at my wit's end! Can you suggest what to do next? Thank you!

Call in another electrician and have him meet with the power company, there is a loose connection someplace.

If this is that elusive, either the utility and/or the electrician can connect a power recorder at specifc locations to determine if and when this flickering happens, to confirm it is occurring and help troubleshoot and pin down the location of the problem.