Ziz said:

I used WinRAR, just like I did for the DVD-5. Should I start over with the RAR files? Create a new ISO and unpack it with PcgEdit instead?

Yeh, start over with the rar files but you will need to mount the ISO file DO NOT unpack with winrar because this can sometimes screw the files up. Download and install DaemonTools from HERE
Once installed restart you computer. Once restarted you will see a Daemontools tray icon in bottom right hand side of your screen (by the clock). Right click on it and goto "virtual cd/dvdrom" and select number of drives as 1 (if this isn't already set. The do the same thing again but this time select "mount image and select your iso file unpacked from the rars. this will create a virtual drive. Now goto "my computer" and explore the DVD and drag all the folders into a new folder (as described earlier) then do all the steps i mentioned to apply the fix and create the new iso. If you still get an error in PGCedit then i'm afraid there's nothing more i can do to help you

You actually never have to unpack an ISO (you mentioned you did that with the DVD-5). Nero burns ISO files and you should always burn the ISO because that way you can make sure that the disc structure is the way it is intended