We are having some problems with the AC in our house and I wonder if
some of you can give me some idea what might be causing it.

We first noticed it to be lights flickering, and I thought it might be
some neighbor using some heavy equipment or something. Then a few days
ago while working on the computer I noticed my DSL modem and router
just power cycled for no reason.

So I went out and bought a UPS, and at night during 8-12pm, I can see
the UPS kicking in every now and then and goes back to AC power. So
something's wrong.

I took out my voltmeter and measured it, much to my surprise, one of
the AC lines is 90v and the other is 150v. In my room, one of the lamp
is very bright while the other one is dim.

After about 12pm, it sort of gone back to normal, both lines register ~120v.

Could a neighbor using some stupid equipment be causing this voltage
drop and increase? Has some equipment in the local electrical company
gone bad? The problem is not consistent, sometimes it happens and
sometimes it doesn't...

Thanks.

Raymond