Help! I tried to burn a movie in iMovie HD and got this message: "No Disc Burning Drive Found. If you have an apple-supported disc burner please check your connections and try again." When I put a disc in the Superdrive I get this: "You inserted a blank DVD. Choose an action from the pop-up menu or click ignore." But whatever option I choose I get: "This disc cannot be used because it is not recognized." I've been Googling this problem all afternoon but the only people who seem to have solved it are Western Digital external drive owners (I have an Iomega 500GB USB2 that I bought from the Apple store) - once they delete a particular file everything is fine, but that file isn't on my iMac! I can play DVDs no problem, so I haven't a notion what this is all about. Can anyone help? Thank you.