Nero Showtime problem

When I insert a DVD into my pc, aprompt comes up that asks with which media would I want to play the DVD, I choose Nero Showtime and it opens up but nothing happens after that so I click on the select source tab and choose the D drive option which is for my DVD player, still nothing happens, I try clciking on the play button, still nothing, whenever I click on the play button though, I notice that the shwotime sceen flickers for a split seocnd and when I click on Eject Disc, it does eject the DVD, any ideas anyone? Thanks.