You need the libdvdcss packages to watch DVD's. It's the thing that decrypts the stuff. They not included with the CD's cause of export laws or something. Just go get them from wherever you get RPMS for Fedora 6. Should be able to find them on http://rpmfind.net
Matter of fact, if I recall, first time to launch Totem, there's a dialog box that tells you what you are missing. But I'm sure most just burn through this screen and click next. I know I did, lol.
Hope this helps.