While searching, I have come up with very little. The three things I will say are as follows...
1) Are you using imgburn? It is the recommended burning program for this activity.
2) Maybe you should try USB loading. You can use the NTFS link in my signature, or you can use FAT32 (generally more used) to play all of your backups from a single USB device.
3) Is your wii able to play burned media? Wiis manufactured after the second half of 2008 (or so, still up for debate) or that have been refurbished with new disc drives cannot play burned DVD media. Confirm if this is accurate or not, and if this is the case, then option 2 above is your only alternative.