At the web I found, lotsa informations about people also having trouble with the named KRUPS device.
Most problems are – like mine – with the Start-Button.
I lost my one some day after pressing.
Here is my introduction for self repairing the device:
To open the device I used a very good explanation http://onthebackside.blogspot.de/2008/05/krups-gvx2-coffee-grinder.html
Watching inside obviously the construction of the button was very cheap made.
So I made an own holding for the button, with a cutter, an old kind of a credit card and hot glue.
Since this the device looks and works better than before.
See my pictures for explanation :
Red arrow = old one
Green arrow = new one