The installer tells me that it couldn't find a vulnerable IOS or something? What's that about?
The HackMii installer is the only program that can automatically make non-trivial system modifications on all Wiis. It has several different code paths (aka exploits) that it uses to do this; on any given Wii, the installer will scan your system to find the most appropriate one to use (generally, the most stable or least invasive one).
If you have recently installed an official update, this may mean that all of our existing exploits have been patched; in this case, please wait patiently for us to update the installer.
In most cases, however, this means you have installed some sort of "mod pack" (we refer to those as "failpack") which leaves your system in a damaged state that interferes with our system scan. In particular, "cIOSCORP" is known to be problematic because some idiot decided it would be smart to take some old version of IOS, change the version number, and overwrite all other IOSes. Other failpacks are less destructive, but that still means its not a good idea to use them.
You're basically on your own, for the sake of your Wii: get rid of the failpack.