Head unit cut out

I just hooked up a new head unit (Pioneer Deh4750) in my mates delica van. The head unit ran for about 3minutes and then suddenly cut out and now wont go. Not sure why this happened. I have installed a lot of pioneer headunits in the past and this has never happened. The head unhit itself appears to be still runing pefectly and the a small click can be heard when the head unit is turned on (coming from speaker) but other than that no sound comes from the speakers.
What can i do?????
Thanks