Sorry for the deferred response; this thread has been started in a wrong section and thus went unidentified. I have moved your post to the right section and you will be assisted by our experts soon.
my assumption is that you could have a dropper in memory that keeps re-copying a file that Virusscan OAs detects as trojan downloader.
I recommend you set up a User-configured Access Protection rule with Notify only for the folders that you see VirusScan is detecting the trojan in.
After some time and some new detection popups, you would review the AccessProtectionLog.txt in %DEFLOGDIR% folder to see what exactly are copying the file there.
From then on you woud take an action on that file (for example deleting it by hand or making sure it does not load in memory again, etc.)
That System Disconnect from network and run ON DEMAND SCAN. I hope it's clean and won't popup.
Pls Upgrade latest version make sure latest patches and updates,