You migth be able to use the Maintenance mode, that's holding - and + and stabbing at A a few times.
It's strange for a Wii to fall sick after some weeks without any changes. Are you sure you haven't installed a bad game channel or something, because that's what it sounds like.
Are you able to autoboot games? Filling the Wii NAND with game saves and stuff from every game you could lay your hands on can also boot you into data management.
The most useful application to boot would be Any Title Deleter or even better ATD Mod.
You can try to re-install IOS30 v1040 and System Menu v289 and see if that works, that'll be something you can do via Wad manager. Uninstalling a bad wad however is tricky unless you know which one it is.