This also comes when my Antivirus´ Autoprotect (i use Norton) is disabled so i dont really understand the defective antivirus
The message is quite clear, and as I've said (and also the message said), it's caused by a defective antivirus that is blocking the installation.
Norton is probably the worse offender when false positives are concerned, because it's based on a flawed concept of a file having a "reputation". Since we update files so often, they will never be able to gain enough "reputation", so they are blocked by default.
You must correctly disable the antivirus while installing and/or disable the FSX folder from scanning. Try to disable every option that relates to real-time protection.
The real solution, of course, would be switching to a more reliable antivirus, one that doesn't mistakenly block legit files from installing (not even mentioning it's trying to block a *.dat file, which is not even an executable!).
For example, the default Microsoft Antivirus ( MSE or Windows Defender in Windows 8 ), doesn't mistakenly identify any of our products as threats (of course, since they obviously aren't...) and doesn't require any special configuration to install them.