okay, in your case, with ModMii, just tell it that you have never modded your Wii (pretend it's virgin) and follow the instructions that way. It will overwrite your broken softmod with a new, working one.
Thanks for the suggestion. I tried this too (even reinstalled Homebrew) with the same results. I assume the nand backup it had me do was too late, since I had already modded the wii. I also tried PimpMyWii in desperation, but although it ran through and said everything was good, it too fails on every game. I don't get it. When using UsbLoader GX and running Mario Kart, I get a 001 error, and on other games, I've seen a 002 error. When using UsbLoader CFG, i just get a black screen.