Sounds like you downloaded the torrent from myspleen.
While I'm no fan of Nero, in this particular case Nero is right -- those VIDEO_TS.* files are b0rked.
I've got different (working) IFO/BUP files from when that disc was uploaded to Usenet group alt.binaries.starwars
Send me a private message (PM) if you'd like to try them.
Be sure to enable PMs in your user profile (they're off by default) then click my padlock icon beside this message.
Re: alternatives to Nero
I like Jorg Schilling's open-source mkisofs and his freeware cdrecord-ProDVD but I'm running Linux so your mileage may vary....
For a bit more info about this problem check out my message from February 28 in this thread.