Firstly - big thanks for this module - its a fantastic addition, very much appreciated.
Currently I have hit a similar problem twice in the last week using the latest stable emfield and this.
For Vimeo I thought there was a problem using imagecache to process the stored videos as I have always done in the past..... I can set the default view for the content type (or a view) to show me a thumbnail image processed by the module - but not a custom imagecache version.
After some investigation I'm pretty sure that the module is no longer able to take a copy of the Vimeo thumbnail image and is defaulting to the generic vimeo.com version. I have the settings activated to store the images - and if I put a Youtube node next to my Vimeo node it stores the thumbnail fine.
If I do a dpm($node) I can see that under the YouTube array field_video['data']['thumbnail'] I can see the url of the thumbnail is pointing to the settings folder..... however - the similar array for Vimeo just points to a Vimeo.com url - no matter how I tweak the settings. Its almost as if they have write protected the thumbnails stopping them from being copied across??
Maybe I'm overlooking something here - but from previous threads it sounds like Vimeo might be prone to moving the goalposts from time to time - could this be the problem?
Any info would be appreciated - can anyone else replicate this issue - or let me know if they dont get it so I can keep investigating.... and can post back if I source the issue.