SYMPTOMS
Hotlink protection is enabled on domain and .swf extension is added to the list of exceptions.
However .swf files are not loaded with browser. Disabling “Show friendly HTTP error messages” option in browser allows to see Overlapped I/O operation is in progress error
RESOLUTION
Please download the following file:
https://download1.swsoft.com/Plesk/Autoupdate/Windows/8.2.0/123026/hotlinkprot.dll
and place it to %plesk_dir%\isapi folder replacing original file.