Two updates, that were part of January's Patch Tuesday for Windows 7 and Windows Server 2008, make that users are unable to access shares from Windows 7 clients. Also remote connections over RDP, and access to SQL Server 2016, failed for the affected users.
The problems appear to have started after update KB4480970 and KB4480960 were installed. Uninstalling both updates also fixes the issues.
Microsoft did mention in the release notes of KB4480970 that the network interface controller may stop working on some client software configurations. According to the software giant this happens because of an issue related to a missing file that contains OEM information. Unfortunately Microsoft doesn't know the exact problematic configurations at this moment.
The issue is also not new, Microsoft has listed the issue with certain OEM network drivers in Windows 7 roll up updates since April 2018.
German Günter Born reports that the issue appears to be related to a faulty SMBv2 connection which appears to happen if an administrator user is the owner of a network share. When a regular user is the owner of the share and a user with a regular account tries to access the share, the problem doesn't appear to happen.
Born also provides a workaround, this involves changing a registry key through the command line by typing; reg add HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\system /v LocalAccountTokenFilterPolicy /t REG_DWORD /d 1 /f.
After a reboot, the network shares should work as intended again.
