Here's what I'd tried if I were you, in that order:
Go to device manager and select your NIC card. Select properties, then power management. De-select "allow computer to turn off this device to save power". Reboot and try to reproduce.
Open this page, check your OS version, check your event log for the event “Source: LsaSrv Event ID: 5000”, if everything matches, install the supplied hotfix. Reboot and try to reproduce.
Same with this hotfix — check OS version, check your event log, apply the hotfix if it fits.
Set DefaultEncryptionType registry value as specified here. However please keep in mind that this one is risky, esp. if the server is a DC. Make sure you have a fresh backup, and physical access to the server.