I and one of my students are having network problems that we have traced down to our AC.
In my case I have a window AC in the computer room in addition to the central air. It is the window AC that causes the problem. Every time the compressor kicks in the DSL modem resets.
Looking for a quick and dirty solution I picked up an old (dead battery) UPS from school and put it between the power line and the DSL modem but it did not help. I am thinking the low end UPS drives the AC out from the power line when there is power.