For everyone having problems with the Chapter Preview Icons not showing correctly, there is a fix for it. It is not difficult if you follow the directions closely, but please do not attempt it if you do not feel confident:
If your chapter preview icons are not displaying under Windows 7, this process will restore them. Please note, however, that you will have to re-import your videos and re-create your workouts since this resets your Workout Blender. This process is only necessary once, so once your previews return you should not have to repeat it.
1. Exit the Workout Blender, then open your Control Panels and choose "View by: Small Icons" in the upper right corner.
2. Click to open "Folder Options"
3. Click on the "View" tab at the top of the Folder Options window that opens.
4. Under "Hidden files and folders" in the list of Advanced Settings that appears, click on "Show hidden files, folders, and drives", then click "Apply" at the bottom of the window.
5. Leave the window open since you will need to reverse this process in a minute.
6. Navigate to the folder: "Your Hard Drive" > Users > "Your User Name" > AppData > Roaming and drag the folder "Cathe" into the Recycle Bin and you can close all the folders you opened.
7. Go back to the "Folder Options" window and check "Don't show hidden files, folders, or drives", click "Apply" and close the window. You can also close your Control Panels.
8. Restart your computer, then when it is done restarting launch Workout Blender and import a video. The problem with the previews not showing should be fixed.