I would put my money on a bad theme. So, if you don't have boot2 bootmii and priiloader, and don't wan't to buy a modchip, you can fix the bad theme by updating via disc. Get your hands on a gc controller and Super Mario Galaxy 2, then do savemiifrii and put SMG2 into the wii, walk away for awhile, half hour maybe. This will update your wii to 4.2 and fix the bad theme. Of course if that does not work, it must be the channel, in which case you would need to get your hands on a modchip to do anything else. But I really don't think that channel you linked to is bad.
Ipsa scientia potestas est.
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Be careful though, if you do what mauifrog said and you have bootmii as boot 2 installed it will overwrite it, and you won't beable to use it. Unless you have previously updated past 4.2 and you downgraded.
bootmii wont load and the theme was for ntsc
New mario bros is 4.1 and has boot2v4 on it. Its not just 4.2 or above that gives you v4
i previously had 4.3u then downgraded i cant do save mii frii
How are you trying SaveMiiFrii? Are you taking the controller apart? If not you need to. Look at these pics.
edit: also, it helps a ton if you press the buttons on the controller before you power on your Wii.