It looks like the rear speaker wires have shorted out somewhere. Id check through all your wiring to make sure that nothing is exposed. It would also be an adea to chop the rear speaker wires off the new HU, but leave a little bit and tape it up so if you did want to add new rear speakers at a later stage, you can do so.

Was posted in help, then i realised it shud b here so posted it in ere:o
Its unfortunate but my headunit gave up today!
I was on my way home and went to change the track and noticed it was unusually hot, thought nothing of it till i smelt electrical burning and saw smoke coming out the dash Pulled over and yanked the stereo out to find that it was coming from the back. got home plugged it in and it comes up with a error message, which the book tells me that its fooked! I tested the outputs on the back and it seems the 2 rear outputs have blowned up even tho i have no rear speakers?

i gonna get new stereo this week sometime, jus wanted to know if this could b a fault on my car cos dnt really want to fook up another stereo! There are no rear speakers so should i jus chop the wires at the back on my new head unit to make sure it dont happen agen?