I had the same error with a double layer game. Found out the 4G split size i used was the problem. Try 3G! See http://www.reddit.com/r/wii/comments/l8c1r/noob_question_about_playing_from_usb_hd/ .
Hello. Although i'm not a complete n00b, i don't mind if you treat me like one.
I remodded my Wii with the latest software (followed http://www.wiihacks.com/recommended-faqs-guides-tutorials-only/60921-guide-softmod-any-wii.html , used newer files if found), including d2x v7.
I have a 2TB...
Thank you VERY much Cyan! Great tut. What i wonder: i have Multiman 2.00 and copied a DVD to my external USB HD: VIDEO\\VIDEO_TS (and AUDIO_TS). Multiman/Showtime recognizes some of the files as video-files, but it doesn't recognize the DVD, doesn't open a DVD-menu etc. Your manual index says...