You may be seeing the thumbnails that previous graphic programs created in your Windows Explorer cache.  The behavior I have seen occurs when Windows Explorer tries to generate NEW thumbnails for graphic file types that it has associated with X4.  Files that had been associated with another graphic program and displayed as a thumbnail at some point will continue to display correctly in Windows Explorer.

See my earlier post with instructions on clearing the Windows Explorer thumbnail cache.  Then pull up Windows Explorer and view by thumbnail (forcing the generation of new thumbnails).  Copying (not moving) files to a new folder will also force the creation of new thumbnails for the new folder.

For the record, this is what I see in folders that have have never previously been displayed as a thumbnail view:

 A workaround is to associate the files to another graphic program.  The only problem with that is double clicking on the file in Windows Explorer will open up the other associated program, not X4.

And this is what the same folder displays as when I reassociate the files with my older and concurrently loaded Corel PhotoPaint from X3.  Note the thumbnail dispay actually reflects the file contents now.

Hey thanks! I actually do clear the thumbnail cache about twice a month and this has been an issue since installing X4 several months ago. I have done some experimenting since you replied.

I unchecked tif in Irfanview (which is what enabled tif thumb viewing in the first place) and the thumbs have remained. Come to think of it, I don't think i have restarted my machine in a few days. I'll see how that plays out.

-s