Ambient occlusion dark borders

Hi, I’m new here and i’m also new to blender.
So, I’m modelling a room, everything is ok so far but I have a little problem with the rendering/lighting. The borders between the walls are too dark. I don’t have this problem with luxrender but it take ages to render and i’m planning to do an animation.
here is the result with ambient occlusion(1min):

http://img683.imageshack.us/img683/4188/ambiantocclusion.jpg

and with luxrender (8hrs!!):

http://img525.imageshack.us/img525/4417/default1e.png

If you have any other remark that can help you’re welcome.
excuse me for my english.

You may have the occlusion gathering distance set too small for the scale of your model. The default is 10 BU, which should be plenty if your room is modelled at the usual scale of 1 BU = 1 metre. But if you’ve modelled at a scale of, say, 1 BU = 1 cm without adjusting the gather range you will get something like your picture.

Best wishes,
Matthew

thanks, i’ve lowered the max dist and the result is better. but I’m using now approximate gather method instead of raytrace and I have better results.