Any electricians in the house???

[Rich Riesmeyer]

Ran into a problem today that had me tearing my hair out for hours. New to me house built in 76. I was working in the bathroom and the power went out, GFI plug and lights. Checked all the usual things, GFI wasn't tripped, neither was the breaker. Checked all the breakers at the box with a meter, they are all live. Later power came back on all by itself. Turns out the wife had plugged in a fan in the next bedroom. When she plugs it in the fan works, and the lights go out in the bathroom, unplug and the lights come back on. Anyone have any idea what to check to fix this, besides annoying its probably unsafe.....