I can't seem to download the same app twice on my ipad, however, doesn't mean that it can't happen.Or, do you think that it is the same app but one for iphone and another for the iPad? One that comes to mind for me is Skype. The quickest way to delete an app after it loads is to long press the app until it shakes. When thee apps shake, you will see a small red "x" in the corner to delete it. This will delete it off your iPad until you can remove it completely through a sync with iTunes.
Also, will move this to the help section for better attention.