If you import an animated GIF that shows a blank thumbnail and preview, it is most likely the result of file incompatibility. You can try opening the file in the GIF animation program used to create it, saving it again, and then adding it into Clip Organizer again.
If you import a graphic, such as a JPG, Tagged Image File Format (TIFF), or other photographic format, that shows a blank thumbnail, it is most likely because the graphic is too large and your computer doesn't have enough memory to show the thumbnail. However, the clip has been added successfully and can be inserted in your documents. In order to see the thumbnail, try opening the clip in a graphics program and then resizing it to make it smaller or changing it to a lower resolution, or both. You can then add the new version of the clip.