I have the same problems too. So far, My Wii (WiiMC) is able to read and play DVD-R….with CDFS format, but not UDF format. All my old scratch DVD-R movies data…with format CDFS still works fine on any WiiMC version, tested. But I have a hard time getting the new copy I clones. I brought brand new and same DVD-R disc(Memorex, etc.)…but I can’t get them to burn the same as I did last time. I end up with UDF format now…
I burn the same way as I always did…with ImgBurn, but I guess the Wii doesn’t support UDF format.