I'm not too sure on the exact technical differences between PAL 60 and NTSC, but I know they are similar. At one stage, it was the same, but now it apparently is different. I'm sure the NTSC games that do work on the PAL Wii are because the Wii is set on PAL 60 mode. If you read the official Wiki, you will find that a lot of games don't work properly without using the PAL 60 setting. Best just to try that NTSC option out to see if that helps or makes any difference.
22/01/2008
Mario and Sonic at the Olympic Games
Gold Coast, Queensland, Australia