I have also test the Registry Key changes, but doesn't have any impact.
By the way, I just realize that the XP build of my application is using ANGLE (because OpenGL is not supported) and Windows7 is using OpenGL.
By forcing Windows7 to use ANGLE, TeamViewer is working also with Windows7 :)

QCoreApplication::setAttribute(Qt::AA_UseOpenGLES); qputenv("QT_OPENGL", "angle"); qputenv("QT_ANGLE_PLATFORM", "d3d9");

Thanks a lot for your time