Brief
We have modified the 'admin_upload.php' file for version 3.5.
 
Description
In the latest 3.5 version available for downloading when uploading images, you may have received the below error: "This type of file is not allowed."
 
Solution
We would recommend to download an updated version of the file from here: http://www.viart.com/downloads/admin_upload-3.5.zip
 
Further, extract the above mentioned file into the 'admin' folder of your shop replacing an existing one. Don't forget to make a backup copy of the current file in case something goes wrong.

This has still not solved my problem. Is anyone else seeing this problem persist after updating the admin_upload.php file?