I never use wireless kit unless I
really have to. Full of stupid, trivial issues like this - coupled with the recharge factor as well.
Stick with a USB keyboard - cables work.
On this, it could be that the keyboard software was set to automatically update and has applied additional software without your knowledge? Check that in the Device Manager tab that Windows hasn't got a little confused and is detecting several different keyboards now - all with a yellow ! mark next to them?
D.