Issue report and fix provided by Egidijus Jankauskas.

Issue #713 :
When there are no chat windows opened, if Mr Someone is writing you something, you get a notification 
saying "Mr Someone is writing a message". When he finally sends you a message "Hello!", you get a 
notification saying "Mr Someone. Hello!". If you do not focus SC and he writes something else 
subsequently, you don't get corresponding notifications. However, if you click on the chat window and 
then switch to another app again, you start to receive all subsequent notifications.

src/net/java/sip/communicator/impl/gui/main/chat/ChatPanel.java

@@ -427,7 +427,7 @@ public void setCaretToEnd()
      */
     public void requestFocusInWriteArea()
     {
-        getChatWritePanel().getEditorPane().requestFocus();
+        getChatWritePanel().getEditorPane().requestFocusInWindow();
     }
 
     /**