Camera Won't start up.

I know this may sound stupid but have you tried charging the batteries with a different battery charger, it could be the case that the mains charger is not charging the batteries properly and reporting them charged when they are not.. I've seen this happen so many times with DSLR's..

If you've verified that the batteries are indeed charged properly and functioning as they should you can inspect the battery compartment for anything stopping proper contact with the battery terminals.