Today for some unknown reason suddenly my Logitech Wireless Keyboard and Mouse - Model Number EX100 stopped working and very stubbornly denied to work despite my repeated attempts on all obvious and logical steps - resets, battery change and such.
Logitech Cordless Desktop EX100 (920-000879)
After trawling through the internet for some time I figured that I am not alone in facing the issue but surely have been hit quite late by it. It appears Logitech was more than happy to replace it at one point.
Anyway, further forum hopping lead me to a post that felt like a very unlikely solution but I gave it a shot and should I say more? It worked indeed. So this post is not only for world but for my future reference.
With thanks to "Andromedia" on logitech forum, I present the solution that resurrected my dead keyboard and mouse.
That should do the trick. At least for me it did. :)