Nintendo has issued a new system update today that (reportedly) deletes any custom channels you have installed via the homebrew channel. Along with any custom channel the update will also delete any tweaked save data like the Twilight Hack as well.

Homebrew community notice:
At this time, WiiBrew recommends that you do not update your Wii through Nintendo, as it disables some homebrew (DVDx, PatchMii). Recent reports suggest System Menu 3.4 removes all custom channels.

However, for non-homebrewers the channel is said to add enhances parental controls, USB keyboard support for Mii Channel, and other ‘system functions have been improved’. Along with that Nintendo has also changed their service privacy policy for system updates.

UPDATES AND UPGRADES
We may without notifying you, download updates, patches, upgrades and similar software to your Wii Console and may disable unauthorized or illegal software placed on your Wii Console to ensure that your Wii Console is operating properly and efficiently, comply with applicable laws, assist law enforcement, protect us and our customers, or prevent the use and distribution of software obtained through improper channels.

Way to go Nintendo.