Just for a change say Yes, allow it to reboot and see if that clears it.
If nothing has changed.
Operating system restart needed by avast message - First check the contents of the C:\Program Files\Alwil Software\Avast4\Setup\setup.log file, which should show you why it thinks the reboot is needed.
This could be solved, in some systems, by deleting the file C:\Program Files\Alwil Software\Avast4\Setup\reboot.txt