I am using Windows 8.1 on two notebooks at home and also use Windows Phone 8.1 on my smartphone. On the on the PC at office, I also have the same OS, but with a different behaviour concerning screen-saver screen. I never saw a similar problem on another Windows computer.
The problem is subtle and will not be recognised by any user who is not multilingual. As I write often in several languages, switching from one keyboard to another swiftly, it is too too tedious for me to do this with the mouse. So, I use since older Windows versions the shortcuts for keyboard keys: [Ctrl] + [Shift] +  for German, [Ctrl] + [Shift] +  for English, [Ctrl] + [Shift] +  for Turkish, …, and [Ctrl] + [Shift] +  for Arabic. This works also in Windows 8.1, but not properly on the PC at office - an hp computer where Windows 8.1 has been installed later on.
My problem is that after a [Alt] + [Ctrl] + [Del], all the saved shortcuts are all of a sudden "forgotten". This is even the case, if I immediately press [Esc] after entering the screen where to select to log off etc.
What happens after an [Alt] + [Ctrl] + [Del]? How can such a strange behaviour occur? I use a Windows account for business purposes here on this PC, i.e. not my private account. Have you ever heard or read about such a problem?
Thank you for your help!