“The trust relationship between this workstation and the primary domain failed” — recently when I logged into a PC running Windows 7

• https://support.microsoft.com/en-us/kb/2771040
• https://support.microsoft.com/de-de/kb/2771040

When I tried to login again to my Win7 PC at work after lunch:

In English:

The trust relationship between this workstation and the primary domain failed.

In German:

Das Vertrauensverhältnis zwischen dieser Arbeitsstation und der primären Domäne konnte nicht hergestellt werden.

I tried WIFI, and it worked. I tried my colleague’s docking station, and it worked. Swapped ethernet plugs, and it worked. I used my own docking station again, and it worked, and apparently the problem had disappeared.