Replying to IMovie HD/ gopro help!

Hey guys I am just starting to get into some basic editing and I have found a problem.

I am using all clips from gopro r3 (720p @60fps)
I am editing in iMovie HD

When I create a project I chose the 720 HDV option. Import my clips, edit some stuff. I can do all of this fine, the problem comes to saving my movie I created. I go to "share" and choose the quicktime, full quality option. It saves and works perfectly on my computer, as a .mov file. However I just tried to upload it to youtube and I get an error that says it can not identify the video codec and will not upload. I don't know what this means....

I went back to my project and clicked share, quicktime, CDROM. It creates my .mov file with shittier quality. Again, plays fine on my computer. I go to upload this to youtube and IT WORKS!. Why does this shitty crappy quality version work, but my good quality one will not? How do I get my good quality one to work?

I really appreciate any and all help guys! thanks