What games are you trying to play? Is your wii hooked up with AV or component cables? I use gx on an ntsc wii and tv with component cables and I've never had a problem running pal games. I've done force NTSC never touched the Vidtv patch
I ran into that yesterday with marvel ultimate alliance and I ran the ISO through wii scrubber and then it worked, did it on some other games, one I had to scrub twice before it would load to the hdd but they all eventually worked