If you don't feel like monkeying around with the phone just take it back. Within my 30 days if the phone even smells funny to me I'll take it back. It just so happens that my evo is one of the few perfect ones out there. Go get yourself a perfect one, too.
Your second choice is to wipe it, restore all your apps, etc and see if that works. If it doesn't, you go with step 1 above, and restore your apps all over again.