I wasn't sure where to post this but I had this problem and looked all over for an answer before eventually asking here and still not finding it. A lot of people are getting stuck on this screen. What worked for me couldn't be more simple.

I tried a few different USB loaders that I found and installed but the only one I could get working was USB loader GX (Haven't tried Wiiflow yet). It's the same with the game "Just dance" if you can't get it to load up and it also fixed my wii sports resort problems from loading it from a HDD too.