Can you post the CSS for your site? If you search this forum for drawing and offset issues you'll find some older threads that had problems which boiled down to markup structure (drawing toolbar being created inside the map content pane) and/or CSS.
Nothing jumps out at me...what's your markup look like?
Markup meaning your actual HTML for your page. Can you post your HTML for your page?
<div id="map" data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region:'center'"> </div>