ARGH! Pioneer sub acting wierd

hi,
I've installed a pioneer active sub (it's a TS-WX10LPA) last week, after
only being in about 7/8 days, it started making a fast thumping noise
(duh-duh-duh-duh-duh e.t.c.) which doesn't stop until I either turn off the
ignition completely or put the face off front on the stereo - wierd eh?

Now, 2 days later the whole thing has packed in and won't work at all. the
power light comes on but the internal light (it's got a kind of viewing
window with a light to illuminate the speaker) doesn't work. I'm completely
at a loss as to what is wrong. I've checked the connections at both ends and
nothing has become frayed or disconnected. I'm very dissapointed. If I send
it back to Pioneer will they replace just the unit? I don't want to have to
take all the wiring out again, I've got it all neatly behind the trim.

Any advice very much appreciated, the sub was bought from MCS Direct.

Cheers.
James