ATC like 78 rpm record on 33

Hi all,I have recently purchased a TFT screen which is connect on my dual output of my NVidea Geforce 4 460MX. When my screen has a lot of white (e.g. flying in the clouds) my ATC sometimes starts to speak very slowly (like an old 78 rpm record played on 33). This problem seems not be connected with disk swap or frame rate changes. Any idea?Some help to solve this weard problem would be appreciatedCheers