Iphone 3GS screen blank

Hi all,

Got my iPhone 3GS yesterday and today the screen went blank!!! It had 40% battery left and just crashed.

I have tried holding down power/home buttons but it doesnt work. I have also placed it on charge from the wall but nothing. When connected to the Computer it is not recognised by the computer or iTunes....

Any ideas?? Support isnt on the phone until Monday.