If you’re using Avira’s Free antivirus and are a mad computer user like me that never reboots his computer (unless something blows up), you might have noticed that Avira periodically updates its program (beside the virus definitions) and asks for a system restart to complete this.
Well, the computer restart isn’t as necessary as it appears, but restarting Avira is indeed the only option for the program to update itself.
All done.