Ronny, I think NAV and avast! need the file to
be in the local disk.
Open the Stardard Shild provider settings and check the sensitivity to 'High' (or, at least, 'Custom' and mark to scan files on open/create/modify). Probably you will see a warning of avast at that time.
If you prefer, add avast into your download manager:
c:\program files\alwil software\avast4\ashQuick.exe
without parameters...
