Index: ui.core.js
===================================================================
--- ui.core.js
+++ ui.core.js
@@ -469,7 +469,7 @@
 
 	_mouseMove: function(event) {
 		// IE mouseup check - mouseup happened when mouse was out of window
-		if ($.browser.msie && !event.button) {
+		if ($.browser.msie && parseInt(jQuery.browser.version, 10) < 9 && !event.button) {
 			return this._mouseUp(event);
 		}