What programs do you have? Photoshop Elements, Premiere Elements, Elements Organizer? And, what version?
What computer operating system?
Where is this directory? Are you saying that, wherever that is, all the tiff thumbnails have images?
And, into where are you importing them where you lose the image in the thumbnail for the tiff file?
Your thread seems to be cross referencing Photoshop Elements and Premiere Elements Forums. Was that your intent?
Add On...where are these tiff files coming from?
Are they flattened or in layers?
Add On...Are the thumbnails that do not appear really not appearing or are they slow to appear?