I ran into this error when my Account was Locked-Out and I wasn't aware of it yet.
I was still logged into Windows at the time, so I couldn't figure out why at first.
Lock your station and try logging back in to see if your Windows Account is locked-out.
Once I Unlocked it, I didn't have to reboot, as the SSMS window (that I still had open)
was then able to Windows Authenticate (but you should still do a reboot).
As other answers state, it could be more than one thing that causes this error message.
