Our database server had run out of disk space, after freeing up some disk space any query run in sql server management studio, with the results sent to grid view, resulted i
Yesterday i faced the same error "The directory name is invalid" when i tried to open New Query Window in SQL Management Studio 2014. It happened after cleaning (deleting) %temp% folder files.
I Restarted SQL services but no luck!
My problem was solved after restarting the server.