iMovie 11' Makes Blurry Videos! HELP!

So my imovie 11' i have had for a while, makes all the videos i import blurry. And even in the preview screen it looks horribly blurry. The videos i upload are mostly 720p or 1080p HD and they stil look SUPER blurry. I use MP4 videos i have downloaded and ones i have recorded off my HD camera. When i export them the still look blurry and basically it looks crap. I thought that it wouldn't bother me at first but when i started using Youtube people did criticise.
PLEASE HELP ME i can't be the only one with this problem!

Hi, are you recording with the imovie built-in camera, or are you recording the screen with quicktime player or something else? Send me a link to one of your videos or add an attachment so I can see what's going on. Here are some of my videos with the imovie built-in camera in HD and also quictime player recordings in HD
Quictime Player recording 1080p: How to Hook Up ps3 or xbox 360 Controller to a Mac - YouTube
Imovie camera 720p: Vlog #1 Christmas is Coming - YouTube
Imovie camera 1080p: Blurble! - YouTube
Are these what yours are turning out like? and also be sure to subscribe to my youtube channel and tell your friends about it