This could happen if the LAN Manager Authentication level setup on the Windows 7 system is not compatible with the Non-Windows 7 PCs on the network. To resolve this problem, quickly check the LAN Manager Authentication level on one of the networked Non-Windows 7 pc and match the setting onto your Windows 7 PC.
To view/change LAN Manager Authentication level,
1. Click Start, search for “gpedit.msc” (Start – Run in Windows XP and earlier). This will launch the Local Group Policy Editor.
3. In the rightpane look for “Network Security: LAN Manager authentication level” and you should be able to see the set level. On a default install, it should be “not defined”. Change this to match or be compatible with the Non-Windows 7 PCs on the network. To change, double-click the entry and choose from one of the listed options. Click Apply and OK.
The defaults of are
Windows 2000/XP: send LM & NTLM responses
Windows Server 2003: Send NTLM response only
Windows Vista/Server 2008 (& 2008R2)/7: Send NTLMv2 response only
This should fix the problem.
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