I have a network with 2 Windows 7 computers (7100), some XP computers and 2 NAS devices (Lacie with embedded Windows) and 1 Mac.
The XPs and the Mac can acccess the two NAS-devices without problems. On my two Windows 7 computers I can see the other computers and the 2 NAS boxes - they show up in Network - but I cannot access them, I get an error message "\\NAS is not accessible....... The Network adress is invalid"
I can accces the NAS from Windows 7 thru my browser thru http: (using the name "NAS").
I can also connect from Windows 7 with Remote desktop Connection
This used to work, stopped on the 1st of September (my backupprogram has given an error message every day since then - I backup to the NAS device.)
I have turned of IPv6, I use a workgroup (not homegroup). I have Netbios over TCP/IP enabled.
I have the same problem on both Windows 7 PCs - and no problems on the XPs or the Mac.
I use Norton Internet Security (2010 Beta) and ThreatFire. Turning them off makes no difference.