Your not giving enough information ... did you soft mod the wii? ... what dashboard is it using? ... I had a similar problem playing Yugioh 5D's for about an hour or 2 on a 4.3 wii, then the wii would stop playing sound and the controls would become unresponsive. Then after restarting the wii without disconnecting the power cord for about 10 to 30 seconds, the wii would power up flicker, and then the screen would go black, I did manage to fix this by updating a few of the cios files and by picking a ios that the Usb Loader couldn't identify directly (posted in the wii u homebrew section, I know the wrong section).
After a few tests after the fix, Yugioh played for more then 6 hours (got tired so couldn't play longer), another session it froze after about 4 hours, then another session it play for a long time too. The Error is probably one of those undetected "BCA" errors that shows up infrequently or bad programming in the game itself.
I think you have a bricked wii, maybe it was bricked by an update, or was exposed to high humidity or moisture at some point and you did not know about it, and it fried some of the internal memory.
(I'm only a partial fan of the wii, meaning I purchased it just to play the resident evil games, yugioh, and some of the shooters, everything else on it is just to boring for me to enjoy, plus I still play my xbox360, occasionally I still do play the wii. Yugioh 5D's (card game) was the only game I had this problem with, and it sounds like yours ... ... since nobody seems to have this problem on a non 4.3 dashboard wii, and its not reported anywhere, I suspect it may only be limited to the 4.3 wii, just like some people who play the "Fatal Frame 4 Translation" on a 4.3 wii have trouble getting it to work without softmoding their wii and attempting to play it through the usb loader, or so I've heard)
(Just off the top of my head, I know that if you set your wii to boot using the "bootmii" folder to the configuration screen and not to the wii homepage, you cannot use your wii mote, but I use this method because you can navigate using the gamecube controller to the homebrew section, and then to usbloader and play a game using the gamecube controller without having to use the wiimote. Or after starting a game then switch to using the wii mote, if the console is bricked it will simply not search for the wiimote and the wiimote will turn off after failing to find the wii console)