Dark shadows on walls and ceilings

[lucy park]

I live in a 8 year old bungalow. 6 months ago, dark shadows started to appear on my living room ceiling. I put it down to the smoke from burning candles and did a total paint job of the whole house. I now have the shadows throughout the ceilings in the house and coming down the inside of external walls, these are focused on where the intenal wall paneling has been screwed on.
I have had 2 major builders come and inspect, they have confirmed it is not being caused by damp or poor ventilation but they cannot tell me what it is!
Painting over it does not work.
Any help very, very welcome as this problem is driving me mad!

[stoneyboy]

lucy park,
Try an application of bleach on a dark area, if this gets rid of the shadow you may well have mould growing on cold areas of the ceiling and external walls.
If this does not help there may have been a fire (with smoke damage) at some time in the past.
end