The wii is easilly fixable by updating to 4.3 via disk. Now you need to be very very careful, it is very possible to brick your wii updating to 3.4, 4.0, 4.1, 4.2- depending on the method you used to downgrade the wii. When you downgraded, did you delete ios50, ios60, ios70 or install functional versions of those ios? If you did not, do not update to 3.4, 4.0, 4.1, or 4.2. You can fix the wii by updating to 3.3 or 4.3 safely if your on 3.2.
If you have a dip patched ios30, like the one installed in my guide or a modchip, you can load a recovery disc to launch any app you like and fix the wii.
You need to use savemiifrii to load the recovery menu.
-Update to 3.3 or 4.3 via retail disc
-If you removed stubbed ios50, 60, 70, update to any sm menu you like via retail disc
-If you have a dip patched ios30 (cioscorp or my guide) burn MMM-250.zip and load it from the recovery menu via savemiifrii. You can also use a modchip to load this disc and other. You would want to reinstall your system ios and system menu to fix the issue. Be sure to install the correct versions.
Beware the stubbes.