I was having the problem where both games would freeze with a green or black screen. After much testing the following worked.
Fisrt My Wii is on 4.0u Via Waninkoko.
I use the USB Loader GX
I have Rev 468
I installed cIOS38_rev13 (not B) all others failed to load both games.
IJ Staff of kings loads right up!
MySims Racing you need to enable the "002 fix" in the games settings.
The first time I loaded MySims I gut stuck with Green screen. I restarted My Wii and it worked every time since. If you try to load covers into the loader the game will not load next time you try. You must restart the Wii.
Now the info above is in no way a guide. But This is what I did and it works.