Umberto, I do not have any computer resident anti-virus, windows defender or firewall (except modem firewall) program on my system and yet I have this problem.
Then you cannot be sure if you have a real virus instead. Maybe not a dangerous virus, but one of those adware-related stuff (loaded by browsers), which might hijack downloads. I seen something like this, of such adware invisible browser plugins, which intercept your PC DNS settings, causing issues with downloads.
But note, I wasn't replying to you. I was replying to the user with the log indicating a outdated Couatl.exe version. In HIS case, the problem is surely he hasn't run the FSDT Live Update OR (if he has), something is blocking it.