It seems BitDefender has updated their Linux version of their virusscanner from 7.5-3 to 7.5-4, which also changes the download URL used by TRK’s virusscan script.
This is a scenario I had foreseen in TRK 3.2. I can adapt the url on the trinityhome webserver so you get redirected to the correct url. It will give you a warning that this url is not the same than the one mentionned originally on TRK.  You can then answer "y" if you want to continue. Unfortunately, it will not continue.
But, luckily, because of another bug in this routine (a stupid typo in my code), the next time you run ‘virusscan -a bde’, it will download the new version of BitDefender after all and continue.

So the message for virusscan with BitDefender is: run it twice.

Next release of TRK has this fixed of course (and better test too).