Nintendo firmware version 4.2 DISABLES bannerbomb. It also deletes the homebrew channel. Update at your own risk. Nintendo released the update September 29,2009. -BKF-

Just to add to that, there is a exploit out however this updates your boot2 to boot2v4 which means, you cannot downgrade your wii, This part of the upgrade is irreversible and would mean your unable to use some stuff in your wii you would like to.

This update also *I think* deletes bootmii as nand, So watch out fellow Wii-Brewers.