Controls Key Problem ( White DOS command list )

[Racetrack]

Hi guys, I know that I'm flooding the Forum with a lot of technical questions, I hope that this info will maybe be usefull for any other pilot!
The problem is this: while I'm flying sometimes I have to press "Shift" maybe to set Airbrake or any other parametres of the plane/bombsight, sometimes when I release it appear an huge white list (seems like MS-DOS) covering all the screen that disable me to do anything with the Sim, the only way to get back to the sim is to re-press shift. This is too frustrating in the middle of a dogfight trying to do a level-bomb raid

How to prevent this problem?