Grainy Audio, sub cut out

Priuschat,

A few months ago, you helped me install a BOSS compact sub in the trunk of my Prius, for which I extremely grateful. All was working very well until recently, when I began to have some issues.

The sub recently cut out. The blue indicator light on the gain knob near my seat is off, and the amp itself shows no indication of receiving any power. All connections are solid, at least on the woofer end.

When I play audio through the aux input off my iPod, the quality is very grainy. (Yes, even with high quality WAV audio files.) When there is a lot of noise during the song, say during the chorus, it gets clipped and sounds very grainy. It was not always this way.

However, when I play music from the CD player, it sounds fine. Still, though, the sub doesn't turn on.

What's going on here?? Do I need to inspect my connections on the JBL amp end of things? I noticed that it may have happened when I ran over a bump; the audio has cut out sporadically in the past leaving me with only one channel after I took a pothole or something similar.

Thanks for any suggestions,
Charlie Tokowitz