I use windows 7 professional, no other virus tools, version 11.1.2245 of avast internet security. And under windows Network I see ReadyNAS Duo [nas-77-85-1C]
Normally it is also listed under computers and I can see directories. Now I only have an under storage. If I click it the netgear software is started. So it looks Avast is blocking listing of that external networkdrive.