I assume you are using, C:\Program Files\Alwil Software\Avast4\ashQuick.exe to scan the downloads.
If so by default the ashQuick scan shouldn't seek any acknowledgement (the whole purpose of a quick scan), so it would appear you have tweaked the settings. Program Settings, Common, Show results of Explorer Extension. If this is checked then you will get the results of any ashQuick.exe scan, it is normally unchecked by default.