I think I know how you may fix that problem, if you have to faces together at that tight angle, with smoothing applied that scenario may happen, I've experienced it. Here are some pics for me to help visually explain.
right bad normals, left fine

showing a closer shot

with edges, you can see the left shape has a face at the end with corrects the bad normals.

better view with normals on, showing the face and the better shape to the right.

I've personally had this problem before and this is what I did to correct the problem, Moach.
