Obviously, the solution is to either repair or simply delete the user.config file, but we have to find it before we can do that. I won't get into repairing, since there's no simple way that I know of to do this. In most cases, deleting the user's application settings, while inconvenient, is not the end of the world, so long as the user is given fair warning that this is about to happen. You're free to take other measures, of course.
It turns out, the path to the user.config file was in the exception all along! But, it's sneakily hidden inside an InnerException, and maybe this is why it eluded me at first. So, allow me to present a block of code that will basically...