SQL Server 2008 Windows Auth Login Error: The login is from an untrusted domain

Another reason this might happen (just happened to me) ... is the user's password expires. I didn't realize this until I tried to remote into the actual server and was prompted to change my password.

The issue was caused by a down Active Directory Server, which of course could not authenticate the Windows account. Thank you for your assistance.

For me, this happened when I edited a blank drivers/etc/hosts file, and added an entry for a local website, but neglected to add 127.0.0.1 localhost