iMovie fails to start

Hello,

I bought a new Mac Book Air OS X 10.9.4 last week and worked smoothly with iMovie until yesterday when it failed to open. I can see the iMovie Menu Bar on the top of my screen but the program itself won't open.

looking for solutions on different forums, i have already tried the following:

• iMovie works perfect when install and log in under a guest account
• I removed the imovie plist-file from my preferences folder in my user library, but it still did not open

To my knowledge, the only difference since the last time I successfully opened iMovie, is that i copied some .mov files on my Mac Book Air which I imported from through my iMac

thanks for all the suggestions/support

regards