Did you install Avast while you where logged in as Administrator?
If not, remove Avast, login as administrator, reinstall Avast.
Have you checked Avast's log file?
If not, do so to see if it tells you more.
Avast does not hold on the system restore folder.
They 5=access denied can mean that Avast was unable to scan file(s)/folder(s), which is normal behaviour if they are password protected archives, or if you have not select to scan archives also or if you don't have the proper permissions for that folder.