Here's the solution guide to fix Nokia 5000 keypad malfunction. In this picture guide its shows the keypads tracing line paths (keypad ways). This repair solution may help if the keypads membrane is okay but the keypads keys does not work or failed to initiate.
This also shows the 5000 keypad IC jumper ways, for temporarily test procedure before replacing with a new keypad filter IC spare parts. Just follow the colored lines on the picture to trace each corresponding lines across the keypad pin connector socket on the main PCB board.