First, check how much pressure you're using and for how long you're pressing on the screen when you're trying to use the URL/search bar - sometimes it's just a matter of pressing firmly. like you would for a long press, but for a short enough time for it to do a long press action (usually copy/share URL dialogue for that sort of thing). Short, quick taps generally don't do it when using the browsers.
If that's not actually the problem and if it's being unresponsive in a way that you can easily reproduce in a variety of apps (meaning it's a problem with the screen), definitely go to Settings -> Personal -> Backup & reset to do a "Factory data reset" and then take it back for an exchange.
Last edited by JD Gumby; 02-03-2013 at 04:23 PM.