I would agree that it sounds like a power issue in your house. I have seen odd power issues causing a variety of audible and visual problems with various A/V and even computer monitors. Some people call it dirty power, and it isn't uncommon, but many times it takes the right combination of power consumption devices.
I just would be conserned that the power may be what is causing your sub to go out, and until it is resolved, you could have problems indefinately.
I agree, try a line conditioner (see if you can borrow one from someplace first), or try the surgeprotector. Many UPS (not the shipping company) units offer surge protection and power filtering in one.
