You can try using on-demand scan (e.g. righclick the file in Explorer and select Scan…). If the file is not detected, please submit it to virus@avast.com for analysis. If the file is detected, though, there’s likely a collision between the two AV’s, although if Standard Shield says it has scanned the file it would be quite weird… Anyway, I’d definitely recommend against using 2 on-acess scanners at once - there is a great chance that sooner or later, your OS will crash… :-\

Thanks
Vlk