What would cause my subwoofer to suddenly stop working?

[MrHT]

I owed the Boston Acoustics CSSUB10B subwoofer for about 9 years and was always happy with it. I live in an apartment, so it delivers enough bass for me in my small home theater. But the subwoofer seems to have stopped working recently.

The funny thing is, it still turns on and receives signal. I can tell because it has an auto on/off feature so it detects when a LFE signal comes in and turns on automatically. And it still does just that, but no bass comes out of the sub anymore. Nothing whatsoever, even tho I played with the volume dial.

How the heck can a subwoofer die like this suddenly? Now, I'm very concerned that maybe one of my Polk Audio speakers would just mysteriously die one day.