IE has had this problem for the longest time (I'm assuming you are using IE + Adobe plugin).
Easy solution?
theEventtarget.ownerSVGDocument.attachEvent('onmousemove', myMoveHandler);
Or if the Adobe plugin exposes a DOM2 Events model:
theEventTarget.ownerSVGDocument.addEventListener('mousemove', moveHandler, false);
You basically attach the move handler to the document, as opposed to the element.