Try changing the fuse in the mains power supply. Otherwise, it may be as simple as the power supply being shot or more complex. In the unlikely event of you knowing someone with a compatible mains lead, see if you can borrow it to rule out that as the problem (or possibly find out that it is the problem).
If not, try taking it back to the place of purchase and getting them to check. Be firm - in my experience most retail warranties are rubbish and the store will try their best not to do anything.