Thanks for the input, everyone. I also wonder if it has to do w/ file permissions--I noticed some of the files (like .mpls and .m2ts and .clpi) were not set as executable on the filesystem for ROTJ, but they were on episodes 4 and 5. So now I've gone thru every folder within BDMV and CERTIFICATE and made sure all the file permissions are exactly the same between the movies.

When I get home, I'll try burning again w/ UDF format. Fingers crossed.

(and if that doesn't work, I'll probably try the WINE/Imgburn method)