I visited last year, July 18th 2011 about this same issue. At that time the power switch stopped functioning. After cycling it a few times it started working again normally. You suggested that I leave it switch to the on position...which is where it has been since.
When I left for vacation recently, I unplugged the sub. When I returned, the sub would not turn on after plugging it in. I cycled the switch a few times with no result. Checked the fuse and it is okay.
The last time you had the problem with your subwoofer it was caused by a faulty signal auto detection, which is easily bypassed by leaving the switch to the on position.
The current problem you have now may not be the same; does the LED on the back of the amplifier turn on? If so what color is it? Try plugging your subwoofer directly into your DvD player (volume at min and slowly increase it), do you get any output?