Hi,
I have the same problem with Squarespace Video Pages: My latest videos suddenly appear blurred even when my settings on VIMEO ('hide from Vimeo') are the same for all videos.
As I'm not uploading the Video directly to Squarespace I'm not even able to change the thumbnail settings (this is so stupid by the way!)
The only difference I'm observing is, that the older videos don't appear as a thumbnail (it's a black screen telling 'due to privacy settings it's not possible to show the video') while the newer videos appear as a thumbnail, but blurry!
Please help....
Jeanette