diff --git a/build/css/ox.ui.css b/build/css/ox.ui.css
index 876a8292..71814648 100644
--- a/build/css/ox.ui.css
+++ b/build/css/ox.ui.css
@@ -97,6 +97,8 @@ Dialog
     top: 24px;
     height: 100%;
     padding: 16px;
+    font-size: 12px;
+    line-height: 16px;
 }
 
 .OxDialog > .OxButtonsBar {
diff --git a/build/js/ox.ui.js b/build/js/ox.ui.js
index 746f05e5..d03099d5 100644
--- a/build/js/ox.ui.js
+++ b/build/js/ox.ui.js
@@ -443,9 +443,9 @@ requires
                         data: options.data
                     });
 
-                function callback(data, callback) {
+                function callback(data) {
                     delete requests[options.id];
-                    callback(data);
+                    options.callback(data);
                 }
 
                 function debug(request) {
@@ -476,20 +476,21 @@ requires
                 }
 
                 function error(request, status, error) {
-                    var result;
-                    console.log("error", request, status, error);
+                    var data;
+                    Ox.print("error", request, status, error);
                     try {
-                        result = JSON.parse(request.responseText);
-                    } catch(e) {
-                        result = {
+                        data = JSON.parse(request.responseText);
+                    } catch (error) {
+                        data = {
                             status: {
                                 code: request.status,
                                 text: request.statusText
                             }
                         };
                     }
-                    options.callback(result);
-                    if (result.status.code >= 500) {
+                    if (data.status.code < 500) {
+                        callback(data);
+                    } else {
                         var $dialog = new Ox.Dialog({
                                 title: "Application Error",
                                 buttons: [
@@ -504,14 +505,16 @@ requires
                                     {
                                         value: "Close",
                                         click: function() {
-                                            $dialog.close();
+                                            $dialog.close(function() {
+                                                callback(data);
+                                            });
                                         }
                                     }
                                 ],
                                 width: 400,
                                 height: 100
                             })
-                            .append(request.status + " " + request.statusText)
+                            .append("Sorry, we have encountered an application error while handling your request. To help us find out what went wrong, you may want to report this error to an administrator. Otherwise, please try again later.")
                             .open();
                         Ox.print({
                             request: request,
@@ -540,7 +543,7 @@ requires
                         data: data,
                         time: Ox.getTime()
                     };
-                    callback(data, options.callback);
+                    callback(data);
                 }
 
                 if (pending[options.id]) {
@@ -554,7 +557,7 @@ requires
                     };
                     if (cache[req] && (options.age == -1 || options.age > Ox.getTime() - cache[req].time)) {
                         setTimeout(function() {
-                            callback(cache[req].data, callback);
+                            callback(cache[req].data);
                         }, 0);
                     } else {
                         pending[options.id] = true;