I finally got workink my cheap usb tv tuner in Ubuntu too.I think the same driver for my webcam makes the tv tuner work too.
But there is a trick too(like always in Linux),you can't have working in the same time both of them:webcam and the tv tuner;one or the other. So when you want to watch your tv channels you must have the webcam unplugged.
Edit: http://mtuxland.blogspot.com/2008/11/ho ... -time.html .