When you are in a Clean Boot state, all third party services/applications are disabled so we can determine if the issue you are having is Microsoft related or 3rd party related. It's usually the later. Or are you saying that you can no longer type them in Normal mode either?
My approach was to determine if things work in Clean Mode. If we can establish that then we can start other programs in batches to see which one is causing your issue.
I can type most normal letters but it's just signs like the EUR sign, sometimes my "@" and " keys get mixed up and others like that. I think it is something in the keyboard settings.