diff --git a/content/events/src/nsEventListenerManager.cpp b/content/events/src/nsEventListenerManager.cpp
index 4f1c075847a..abe803517fd 100644
--- a/content/events/src/nsEventListenerManager.cpp
+++ b/content/events/src/nsEventListenerManager.cpp
@@ -1515,25 +1515,22 @@ nsresult nsEventListenerManager::HandleEvent(nsIPresContext* aPresContext,
           // Try the type-specific listener interface
           PRBool hasInterface = PR_FALSE;
           if (typeData)
-            ret = DispatchToInterface(*aDOMEvent, ls->mListener,
-                                      dispData->method, *typeData->iid,
-                                      &hasInterface);
+            DispatchToInterface(*aDOMEvent, ls->mListener,
+                                dispData->method, *typeData->iid,
+                                &hasInterface);
 
           // If it doesn't implement that, call the generic HandleEvent()
           if (!hasInterface && (ls->mSubType == NS_EVENT_BITS_NONE ||
                                 ls->mSubType & dispData->bits))
-            ret = HandleEventSubType(ls, *aDOMEvent, aCurrentTarget,
-                                     dispData ? dispData->bits : NS_EVENT_BITS_NONE,
-                                     aFlags);
+            HandleEventSubType(ls, *aDOMEvent, aCurrentTarget,
+                               dispData ? dispData->bits : NS_EVENT_BITS_NONE,
+                               aFlags);
         }
       }
     }
   }
 
-  // XXX (NS_OK != ret) is going away,
-  // (aEvent->flags & NS_EVENT_FLAG_NO_DEFAULT) is correct
-  if ((NS_OK != ret) ||
-    (aEvent->flags & NS_EVENT_FLAG_NO_DEFAULT)) {
+  if (aEvent->flags & NS_EVENT_FLAG_NO_DEFAULT) {
     *aEventStatus = nsEventStatus_eConsumeNoDefault;
   }
 
diff --git a/dom/src/base/nsGlobalWindow.cpp b/dom/src/base/nsGlobalWindow.cpp
index 129c90b6705..ac4db4960d4 100644
--- a/dom/src/base/nsGlobalWindow.cpp
+++ b/dom/src/base/nsGlobalWindow.cpp
@@ -5025,7 +5025,6 @@ GlobalWindowImpl::RunTimeout(nsTimeoutImpl *aTimeout)
   nsTimeoutImpl dummy_timeout;
   JSContext *cx;
   PRInt64 now, deadline;
-  nsresult rv;
   PRUint32 firingDepth = mTimeoutFiringDepth + 1;
 
   // Make sure that the window and the script context don't go away as
@@ -5124,10 +5123,10 @@ GlobalWindowImpl::RunTimeout(nsTimeoutImpl *aTimeout)
 
       nsAutoString retval;
       PRBool is_undefined;
-      rv = mContext->EvaluateString(nsDependentString(script), mJSObject,
-                                    timeout->mPrincipal, timeout->mFileName,
-                                    timeout->mLineNo, timeout->mVersion,
-                                    retval, &is_undefined);
+      mContext->EvaluateString(nsDependentString(script), mJSObject,
+                               timeout->mPrincipal, timeout->mFileName,
+                               timeout->mLineNo, timeout->mVersion, retval,
+                               &is_undefined);
     } else {
       PRInt64 lateness64;
       PRInt32 lateness;
@@ -5140,9 +5139,8 @@ GlobalWindowImpl::RunTimeout(nsTimeoutImpl *aTimeout)
       timeout->mArgv[timeout->mArgc] = INT_TO_JSVAL((jsint) lateness);
 
       jsval dummy;
-      rv = mContext->CallEventHandler(mJSObject, timeout->mFunObj,
-                                      timeout->mArgc + 1, timeout->mArgv,
-                                      &dummy);
+      mContext->CallEventHandler(mJSObject, timeout->mFunObj,
+                                 timeout->mArgc + 1, timeout->mArgv, &dummy);
     }
 
     --mTimeoutFiringDepth;
@@ -5209,9 +5207,9 @@ GlobalWindowImpl::RunTimeout(nsTimeoutImpl *aTimeout)
       // Reschedule the OS timer. Don't bother returning any error
       // codes if this fails since nobody who cares about them is
       // listening anyways.
-      rv = timeout->mTimer->InitWithFuncCallback(TimerCallback, timeout,
-                                                 delay32,
-                                                 nsITimer::TYPE_ONE_SHOT);
+      nsresult rv =
+        timeout->mTimer->InitWithFuncCallback(TimerCallback, timeout, delay32,
+                                              nsITimer::TYPE_ONE_SHOT);
 
       if (NS_FAILED(rv)) {
         NS_ERROR("Error initializing timer for DOM timeout!");
diff --git a/dom/src/base/nsJSEnvironment.cpp b/dom/src/base/nsJSEnvironment.cpp
index 3600a7858a6..2b3918124b7 100644
--- a/dom/src/base/nsJSEnvironment.cpp
+++ b/dom/src/base/nsJSEnvironment.cpp
@@ -1277,13 +1277,16 @@ nsJSContext::CallEventHandler(JSObject *aTarget, JSObject *aHandler,
 
       // Don't pass back results from failed calls.
       *rval = JSVAL_VOID;
+
+      // Tell the caller that the handler threw an error.
+      rv = NS_ERROR_FAILURE;
     }
   }
 
   if (NS_FAILED(stack->Pop(nsnull)))
     return NS_ERROR_FAILURE;
 
-  return NS_OK;
+  return rv;
 }
 
 nsresult
diff --git a/dom/src/events/nsJSEventListener.cpp b/dom/src/events/nsJSEventListener.cpp
index 05940460e2a..8f592eb36a3 100644
--- a/dom/src/events/nsJSEventListener.cpp
+++ b/dom/src/events/nsJSEventListener.cpp
@@ -100,7 +100,8 @@ nsJSEventListener::HandleEvent(nsIDOMEvent* aEvent)
       return NS_OK;
     }
     //if (mReturnResult == nsReturnResult_eNotSet) {
-      if (eventString.Equals(NS_LITERAL_STRING("error")) || eventString.Equals(NS_LITERAL_STRING("mouseover"))) {
+      if (eventString.Equals(NS_LITERAL_STRING("error")) ||
+          eventString.Equals(NS_LITERAL_STRING("mouseover"))) {
         mReturnResult = nsReturnResult_eReverseReturnResult;
       }
       else {
@@ -197,18 +198,19 @@ nsJSEventListener::HandleEvent(nsIDOMEvent* aEvent)
           beforeUnload->text = nsDependentJSString(JSVAL_TO_STRING(rval));
         }
       }
-    } else {
+    } else if (JSVAL_IS_BOOLEAN(rval)) {
       // if the handler returned false and its sense is not reversed,
       // or the handler returned true and its sense is reversed from
       // the usual (false means cancel), then prevent default.
 
-      PRBool jsBoolResult = !JSVAL_IS_BOOLEAN(rval) || JSVAL_TO_BOOLEAN(rval);
-
-      if (jsBoolResult ==
+      if (JSVAL_TO_BOOLEAN(rval) ==
           (mReturnResult == nsReturnResult_eReverseReturnResult)) {
         aEvent->PreventDefault();
       }
     }
+  } else if (eventString.Equals(NS_LITERAL_STRING("onsubmit"))) {
+    // Don't submit any data if the event handler failed
+    aEvent->PreventDefault();
   }
 
   return rv;