sounds like you still have mapnavigation enabled. Are you disabling it on mousedown?
I did not have set any special properties for MapNavigation. But after Your message I have tried it by edit the map constructor with smartNavigation: false (see below the full code) but this doesn´t help at IE11. The full JS app is attached too.map = new Map("map", {
extent : initExtent,
fitExtent : true,
slider : false,
logo : false,
maxZoom : 16,
minZoom : 3,
zoom : 3,
smartNavigation: false
});
Vladimir