Movieset thumbnails have gone missing.

Hi,

Since recently all of my movieset are now without a thumbnail. It shows the regular blue folder icon. Trying to set movieset thumb shows me the browse dialog, but obviously I can't browse to them because I don't know where and if they are stored on my system. Also, I would rather not have to do this manually for all my sets. Especially because this should work automatically like it has been up until now. Existing and new sets show the same problem.

Please help.

Q.