diff --git a/unpacked/MathJax.js b/unpacked/MathJax.js
index 0e259d5d4..404054945 100644
--- a/unpacked/MathJax.js
+++ b/unpacked/MathJax.js
@@ -3118,28 +3118,35 @@ MathJax.Hub.Startup = {
     MSIE: function (browser) {
       browser.isIE9 = !!(document.documentMode && (window.performance || window.msPerformance));
       MathJax.HTML.setScriptBug = !browser.isIE9 || document.documentMode < 9;
-      var MathPlayer = false;
-      try {new ActiveXObject("MathPlayer.Factory.1"); browser.hasMathPlayer = MathPlayer = true}
-        catch (err) {}
-      try {
-        if (MathPlayer && !STARTUP.params.NoMathPlayer) {
-          var mathplayer = document.createElement("object");
-          mathplayer.id = "mathplayer"; mathplayer.classid = "clsid:32F66A20-7614-11D4-BD11-00104BD3F987";
-          document.getElementsByTagName("head")[0].appendChild(mathplayer);
-          document.namespaces.add("m","http://www.w3.org/1998/Math/MathML");
-          browser.mpNamespace = true;
-          if (document.readyState && (document.readyState === "loading" ||
-                                      document.readyState === "interactive")) {
-            document.write('<?import namespace="m" implementation="#MathPlayer">');
-            browser.mpImported = true;
+      //
+      //  MathPlayer doesn't function properly in IE10, and not at all in IE11,
+      //  so don't even try to load it.
+      //
+      if (document.documentMode < 10 && !STARTUP.params.NoMathPlayer) {
+        try {
+          new ActiveXObject("MathPlayer.Factory.1");
+          browser.hasMathPlayer = true;
+        } catch (err) {}
+        try {
+          if (browser.hasMathPlayer) {
+            var mathplayer = document.createElement("object");
+            mathplayer.id = "mathplayer"; mathplayer.classid = "clsid:32F66A20-7614-11D4-BD11-00104BD3F987";
+            document.getElementsByTagName("head")[0].appendChild(mathplayer);
+            document.namespaces.add("m","http://www.w3.org/1998/Math/MathML");
+            browser.mpNamespace = true;
+            if (document.readyState && (document.readyState === "loading" ||
+                                        document.readyState === "interactive")) {
+              document.write('<?import namespace="m" implementation="#MathPlayer">');
+              browser.mpImported = true;
+            }
+          } else {
+            //  Adding any namespace avoids a crash in IE9 in IE9-standards mode
+            //  (any reference to document.namespaces before document.readyState is 
+            //   "complete" causes an "unspecified error" to be thrown)
+            document.namespaces.add("mjx_IE_fix","http://www.w3.org/1999/xlink");
           }
-        } else {
-          //  Adding any namespace avoids a crash in IE9 in IE9-standards mode
-          //  (any reference to document.namespaces before document.readyState is 
-          //   "complete" causes an "unspecified error" to be thrown)
-          document.namespaces.add("mjx_IE_fix","http://www.w3.org/1999/xlink");
-        }
-      } catch (err) {}
+        } catch (err) {}
+      }
     }
   });
   HUB.Browser.Select(MathJax.Message.browsers);
diff --git a/unpacked/jax/output/NativeMML/jax.js b/unpacked/jax/output/NativeMML/jax.js
index a693afbf0..63a3d5f75 100644
--- a/unpacked/jax/output/NativeMML/jax.js
+++ b/unpacked/jax/output/NativeMML/jax.js
@@ -156,7 +156,7 @@
       this.Mouseout    = HOVER.Mouseout;
       this.Mousemove   = HOVER.Mousemove;
 
-      if (!isMSIE) {
+      if (!HUB.Browser.hasMathPlayer) {
         // Used in preTranslate to get scaling factors
         this.EmExSpan = HTML.Element("span",
           {style:{position:"absolute","font-size-adjust":"none"}},
@@ -173,10 +173,11 @@
     },
     //
     //  Set up MathPlayer for IE on the first time through.
+    //  Get the ex and em sizes.
     //
     InitializeMML: function () {
       this.initialized = true;
-      if (isMSIE) {
+      if (HUB.Browser.hasMathPlayer) {
         try {
           //
           //  Insert data needed to use MathPlayer for MathML output