I had the same issue with my system.
Restarting the ApacheHTTP service worked (which I assume is why a reboot works).
After some checking I noticed that when you do the update via the SMC web interface it doesn't update ApacheHTTP or Tomcat.
I downloaded the latest SMC installer from the ESET downloads pages and ran the upgrade task, which then selected just the Apache related items for update.
After this, everything seems to be running ok, though its not been long since I did that and can't confirm if that has resolved the issue fully as yet.
I had the same issue with my system. Restarting the ApacheHTTP service worked (which I assume is why a reboot works). After some checking I noticed that when you do the update via the SMC web interface it doesn't update ApacheHTTP or Tomcat. I downloaded the latest SMC installer from the ESET downloads pages and ran the upgrade task, which then selected just the Apache related items for update. After this, everything seems to be running ok, though its not been long since I did that and can't confirm if that has resolved the issue fully as yet.