I have Plesk 8.3 and am trying to enable DrWeb in the "Server-wide mail preferences" screen. I selected "Dr. Web" under the "Used antivirus" and click "OK". I get the "Please wait..." message and it gets stuck at that point for a long time and finally I get a "page cannot be found" error on the right side frame of the Plesk control panel. Can you please help troubleshoot and fix this?