The answer is to disconnect the battery and do a system reset, as below. You'll need to disconnect the battery to fix this properly. Here's the 'safe' method - CORRECT REBOOT PROCEDURE FOR BSI Put the driver's window down, lift the bonnet and ensure all equipment is switched off. Ensure all doors are closed and remove key from the ignition. Wait for 3 minutes, disconnect the vehicle battery and wait 15 seconds. Reconnect the vehicle battery, wait a further 10 seconds (do not open doors.). Switch on the side lights through the driver's window. Switch on the ignition and check system's functionality. Hold lock button on key down for 10 seconds. Remove key open & close door test central locking system. Start the engine and complete the system's check. Failure to follow this procedure could result in incorrect operation of many BSI related items. When you've done all that lower each window - then raise each one and hold the button up a fraction of a second. Radio, clock, wiper settings etc etc will all have to be reset but that's as per handbook. Don't panic if the engine fails to start after this - usually locking / unlocking the doors sorts that out. This procedure cures a multitude of sins on the C5. Oddly enough I had to do it quite often on my previous car (a MK1) but have nevr hasd to do it at all on the MK2 With Thanks to Graeme Bruce on Yahoo C5 User Group