Description
There is a typo in the script responsible to show image preview when "Show image thumbnails on Select Image screen" is selected in Global settings.
 
Solution
http://www.viart.com/downloads/show_image-4.zip
 
Download the file above and extract 'show_image.php' in the root folder of your shop replacing existing file. Please do not forget to make a backup copy of the current file in case something goes wrong.