In the last week or so vimeo has changed the way thumbnails are displayed. If you're using videogall to display vimeo videos and the thumbnails are just plain white then try the following:
Either use an FTP client to access the following directory:
Or use the plugin editor in wordpress to edit the file videogallfunctions.php
YOU NEED TO EDIT THIS LINE >>
$apiurl = str_replace("vimeo.com","vimeo.com/api/clip",$video_url);
AND REPLACE IT WITH THIS >>
$apiurl = str_replace("vimeo.com","vimeo.com/api/v2/video",$video_url);
Hope this helps.