For some reason, after changing the core to the Genesis Plus GX core, I got a black screen and none of the console buttons did anything (apart from long-holding the power button shutting the console down). Now, when I try to start RetroArch from the Homebrew Channel again, it crashes on load. I have tried deleting the configuration files, using a re-downloaded copy of RetroArch Wii and formatting the SD card, but I still get a black screen crash on load.
The Wii in question is a PAL-region Wii, with system software 4.3E, Homebrew Channel version “1.1.0 IOS58 v24.32”.
EDIT: Updated HBC to 1.1.2, issue still remains.