Please help! Final cut express

ok so whenever i imported the clips from my camera by log and transferring in final cut everything was fine and i didn't have to render. then for the first time i uploaded clips form a gopro and they all needed to be rendered because of the format. now whenever i upload clips from my other camera (not the gopro) they all need to be rendered. why is that?

also it says i have insufficient disk space for render, so it won't allow me to render, how do i fix that?

Thanks, +k to helpful responses