Add more informative message

app/scripts/popup-core.js

@@ -49,12 +49,14 @@ function setupControllerConnection (connectionStream, cb) {
 }
 
 function setupApp (err, accountManager) {
+  var container = document.getElementById('app-content')
   if (err) {
+    container.innerHTML = '<div class="critical-error">The MetaMask app failed to load: please restart MetaMask</div>'
+    container.style.height = '80px'
     log.error(err.stack)
     throw err
   }
 
-  var container = document.getElementById('app-content')
 
   MetaMaskUi({
     container: container,

ui/app/css/lib.css

@@ -256,3 +256,9 @@ hr.horizontal-line {
   text-overflow: ellipsis;
   white-space: nowrap;
 }
+
+.critical-error {
+  text-align: center;
+  margin-top: 20px;
+  color: red;
+}