Have you installed a cIOS to play backups? that could be why you are getting that message, you could try using the Trucha Bug Restorer if you haven't already installed a cIOS.
Bootmii installation doesn't change the official IOSs as it is written as IOS254. While homebrew may brick your wii, the chances are usually low. There is a good guide to get your wii back to virgin status in the tutorial section. Searching usually solves most problems.