Sorry, I know that a thread already exist with the Title "Failure to connect to System Event Notification service".
But having tried everything in the thread and without any success, I decided that it was important to post the solution that fixed the problem in my case.
I had the problem with Windows 7.
After many hours trying anything I found on the web, I was being reinstalling my BitDefender AntiVirus.
(Because I uninstalled is to allow me to perform a System Restore to a date before the problem occured)
Anyway my System Restore did not work.
Then, while I was reinstalling BitDefender, the problem was still there...
But during the re-installation of BitDefender, the installer told me that I should uninstall MalwareBytes because it could cause conflicts. So I did.
Then after rebooting, and the problem was gone at the next login and then BitDefender finalised it's installation.
So, I strongly believe that it was solved by uninstalling MalwareBytes.
Now, after 4 reboots, I don't see the problem anymore.
But having tried everything in the thread and without any success, I decided that it was important to post the solution that fixed the problem in my case.
I had the problem with Windows 7.
After many hours trying anything I found on the web, I was being reinstalling my BitDefender AntiVirus.
(Because I uninstalled is to allow me to perform a System Restore to a date before the problem occured)
Anyway my System Restore did not work.
Then, while I was reinstalling BitDefender, the problem was still there...
But during the re-installation of BitDefender, the installer told me that I should uninstall MalwareBytes because it could cause conflicts. So I did.
Then after rebooting, and the problem was gone at the next login and then BitDefender finalised it's installation.
So, I strongly believe that it was solved by uninstalling MalwareBytes.
Now, after 4 reboots, I don't see the problem anymore.