A brick is a computing term for useless. The Wii has many possible ways to be bricked.
A semi-brick is the least harmful but still dangerous type of brick.
The settings menu shows an Opera error instead, meaning you can't change settings such as the date and time.
The system settings menu has many different versions for different system menus and regions. If the version is out of version and/or region, the error occurs.
If you change the region of the console, you can fix it. Or you can install files from the NUS.