I get that message when i try to load up a gamecube game with WiiRD and Gecko OS, i have a usb gecko, but it wont run the GC game why?
Are you running Gecko OS (GC version) by using a method of Gamecube Homebrew? Using any method of Wii Homebrew will not work. SD Media Launcher or a Modchip are your choices for Gamecube Homebrew. There are other options as well, such as SDload (Old Action Replay + SD Memory Card Adapter needed) and PSOload, but those most likely will not work on a Wii (one due to firmware; PSOload only works on a Gamecube).
I would get the SD Media Launcher, as it works on firmwares 3.2 and below on the Wii. I'm not sure if it works on 3.3 however.
EDIT: Forgot one important detail, SD Media Launcher is a product of Datel, and can be obtained at:
http://codejunkies.com/Just navigate to the Gamecube page, they sell them without a SD card ($19.99USD), with a 1gb SD card, and a 2gb SD card.