I downgraded my NVidia driver. Windows Update in Windows 8.1 had upgraded it to 326.01, I've downgraded to the latest released one from the NVidia site which is 320.49.
Similar to another poster the extended screen is blank (a bit grey rather than black today) until I push something over to it when it comes to life, i.e. I don't get wallpaper on it after logging in.
|