I have a 1996 E39 540i. When I press the cruise control button, the green lights come on on the dash but as soon as I press any of the buttons on the wheel that control the cruise control, the lights goes off and won't come back on again until I turn the engine off and back on.

Anyone know what might be causing this? My indy garage had a look but didn't know what was wrong, so must be no fault codes on autologic. Am tempted to take it to a main dealer for a thorough check and diagnosis.