Here's a full solution of Nokia X6 keypad problem and failure. This solution shows the complete line tracks for easy tracing particular keys that stop responding including the camera and volume control switches button.
Nokia X3 keypad keys, camera and volume control button switches solution
Each key were group in one line of connection, each connection is filtered by an ESD filter IC. The solution above shows how each certain keys are being connected to the keypad filter IC. There are three keys commonly connected together in one line of connection, therefore if only one or two key is not working, you may consider that the problem lies only on an open path of connection. If there are three and above keys does not work you may considered that the keypad ESD filter is damaged or faulty.