After update to 10, I cannot share any movies to desktop or vimeo

I foolishly jumped-in and updated my copy of iMovies to version 10 and now I am having a problem sharing movies.

It doesn't share either new movies as for converted old movies.

I go to share and select the relevant option, it shows a window with the video details and filesize, I click next and it asks where I want to save the movie so I give it a file name, I then click OK but iMovie returns to the normal view and nothing is exported.

HELP PLEASE

Thanks

Peter