Interior lights automatic switching doesn't work

[fvf]

Some time ago the interior lights in my 2000 estate stopped turning on and off automatically when the doors are opened and shut. This applies to all the four "passenger lights", but not the rear light for the boot which works fine. Also, all the lights work when turned on manually. Also, it doesn't seem to make a difference which door I open or close, so I guess it's not a case of one bad door sensor.

I haven't really investigated what the wiring etc. is like, but I thought I'd ask here first if this is a known problem or if it can be something simple like the bulbs or a fuse?

Thanks,
Frode