Peter:
This can happen when one the 110 outlet that has a GFI, ground fault interrupt, has tripped. This can easily happen in the head, or aft cabin if pushed or bumped. Look for your GFI outlets, the ones with a push button them. I bet one is tripped and is open. If so, it shuts down that side.

Simply reset it by pushing in the reset button right on the outlet. Then the side will power up.
Hayden