Thank you all for your answers. The error was due to a connector that
has lost contact (sorry for my bad english). when opening the keyboard i
could reinsert the connector and now its fine again.
matthias
You lucked out. I replace keyboards about twice a year. Once a key
begins to stick I get pissed off after a few days of that crap, and I
always end up pounding on the thing with my fist. It never fails, I
always bust them in half. They are made so cheaply now, that they are
garbage right out of the factory. When I got my first computer in the
80s, the keyboard outlasted the computer. These days they are meant to
last a year at most. A few years ago I got so pissed at a keyboard I
took it outside and shot it full of holes with my rifle. Then I
poured gas on it and set it on fire. I took pictures while I
destroyed it. One of these days I'm going to make a website with
those pictures.