System Menu 4.2 - WiiBrew
Nintendo FAILS. System Menu 4.2 can brick virgin consoles. GGs. - All is Brawl

So apparently there has been talk of the 4.2 update bricking people's Wiis, even if they have never installed Homebrew. The issues ae being posted on Nintendo's support forums, and deleted if they don't like the way your worded your post.

4.2 deletes Homebrew Channel (unless it has been updated to the new version), gets rid of BootMii, and updates the IOS to IOS70.

So, liek, dun update!