There could be a problem with that particular power strip causing some kind of interference with the 360 controllers. Just the other day my grandma was having trouble with her phone line (loud hissing could be heard on either end of the phone and the dialup internet could not connect.) After an hour or so I discovered that her printer only had to be plugged in to cause the problem (not even connected to her computer.) I took it out and lent her an old spare and the problem is solved until we get her a new printer.
Sometimes there are just the stupidest causes to problems I guess!