Here's what their site says:
File types compatible with the Photo Channel
The Photo Channel can display or play files in the following formats and sizes:
* Image Files:
Format: JPEG, baseline only
Size: Up to 8192x8192
* Video Files:
Format: Quicktime (motion JPEG)(.mov files)
* Audio Files:
Format: MP3
Please Note the Following:
o Some files in the above formats may not work with the Photo Channel.
o The audio components of some video files may not be playable.
o Using an SD Card with slow transfer speed may result in longer load times or irregular video playback.
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So from the above it sounds like it should work with Quicktime but then they immediately turn around and say it may not work with Quicktime. Talk about wanting it both ways...
But to be fair, they go on to say that not all devices are compatible. There's a list here of compatible devices, and if yours isn't on it, you may be out of luck:
http://www.nintendo.com/consumer/systems/wii/en_na/compatibleMovie.jsp
I'm not sure if this will work, but you might want to try to reencode the files to see if that fixes the compatibility issue. Try using something like this, which is free:
Front End Convert Drop 1.1.2
http://www.download.com/Front-End-Convert-Drop/3000-2170_4-10452586.html?tag=lst-0-2
Again, I really don't know if that will work but it's worth a try.
Good luck!!