Updating will not help...
If you don't have trucha in your system menu ios, don't bother to use custom discs too...
If the "system files corrupted" not caused by something installed with homebrew programs then it's more likely it's because, indeed, something got corrupted in your nand. It could be channels or some certain file in your nand...
Newest filling the nand with savefiles trick may help you if it's caused by a bad channel though.
If it's under warranty then remove the chip and send it to nintendo that's what unmodded people due in the same circumstances...
ps: btw, savemii or the gc trick used to get into recovery menu is for those who semi-brick their wii... for other bricks system menu and it's ios should not be corrupted and you either need a 3.2 or lower system menu or trucha bug in your system menu ios... (also trucha bug for the custom disc you'll be using, but that's not a big problem since you can change the ios used by disc to be the system menu's ios). In other words, savemii is useless for those who keep their wii clean & updated.