For those of you that haven't updated...
Use this installer to update your wii to the latest IOS - and keep your homebrew and wii shop channel working. http://wiibrew.org/wiki/Wii_Shop_and_IOS51_installer
"The Wii Shop and IOS51 installer is a very quick modification of PatchMii modified by Muzer that does one thing: It installs the new IOS51 and Wii Shop Channel, without installing the patches to all the other IOSes. This means that as long as you didn't update, you can now install this to use the Wii Shop Channel but keep all the benefits of not having the update."
I've attached a HBC friendly version of this app (created by Matthew_8) which can also be downloaded at the above (slow) link.