Are you saying this is an avast request to reboot ?
If 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 may be solved, in some systems, by deleting the file C:\Program Files\Alwil Software\Avast4\Setup\reboot.txt
If that doesn't resolve it check this:
You can also check this registry entry (right after computer restart):
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager, if it contains "PendingFileRenameOpertaions".
Check its contents and if there's only "reboot.txt" from avast4\setup folder, delete PendingFileRenameOperations, don't delete any other key.
Back-up (export) the registry key before you edit/delete, just in case.