You can check if there are any settings for the webcam if you go into preferences, then go to the video tab and then in the settings tab you might be able to lower the settings, if you can't than the Dell XPS webcam isn't supported, your older logitech webcam should be able to show in the latest beta
http://www.livestream.com/forum/showthread.php?t=7604 if it isn't visible there, please reply.