As discussed in so many other thread, we never suggested to disable the antivirus, because lots of antivirus continue to work even if the "look disabled", but they really aren't, unless the low level service is stopped or are entirely uninstalled.
Which is why, we always suggest, instead, to configure the antivirus to add the whole Addon Manager folder to the Exclusion list.
Do that, and try the FSDT Live Update, and note if you see any errors or messages that suggest a problem when KSDF is updated.
