As per this old post, about a week ago, this has started occurring on my Windows system. Not sure if any modules were updated recently or not, but currently on 15.2.11.0.
While I appreciate the one answer in this post, I can't delete all my rules and recreate them eacgh time ESET updates to a new version (15 to 16? Or even 15.2 to 15.3?). Some of my rules have been in the system since v9 and v10 - which means that the rules survived through MANY application updates.
Like mentioned in the first thread - it's as if the windows are not getting displayed, causing the firewall to just cause all requests to time out. (They do NOT get denied - as a developer, I get a Denied exception when a deny rule is hit, vs when the request times out.)
Existing rules seem to operate fine - it's ONLY requests that would normally pose an interaction from the user to approve/deny.
