Hello Jens,
Done. I've used a clean soft paint brush. The mainboard was not realy dirt, but who knows. After that, I've pushed gently but firmely until a "clic" sounds and the card deosn't move at all. The board are firmely adjusted to socket and, as you said, I can lift the board .
Some pics of the different elements:
Another idea?
Maybe is a simple case of DOA. I'ts anoying, but it can happen.
Regards.