A problem with Norton AV, for years, used to be that if the document was password protected, the AV s/w would wait for you to enter the pwd (otherwise it could not check the document) but the box where you entered the pwd was covered up by something else which the AV s/w put up, something like "checking document for viruses". So you got a deadlock
Well I have to confess I've never run into that one before in the many years I've been viewing NAV/NIS or similar installations, but it certainly sounds like an easy fix would have been possible .....
