Black Text on black Background

I used (successfully) version 8.2 on my PC.
Today when I started Amaya it showed me only black text on black 
background.
I downloaded version 8.3 then and installed it over the previous 
version.
But that didn't help.
The problem remains.

What could be the reason for that strange behaviour?
Any suggentions?

Kindest regards,
    Tobias Besch