B-spline knot vector generation and interpolation (surface)

I am trying to interpolate the data points (of different contours) to get control points of B-spline by parameterization and knot vector generation. When I use the uniform parameterization method with uniformly spaced knot vector, I get the just about desired shape with control points being close to data points, but when I use the chord-length method for parameterization and knot vector generated by averaging technique, the control point I get are very very far from the data points and I get the warning of "Matrix is close to singular".

What to do to use other parameterization method ? How to sort it out.

[Unai San Miguel]

Can you post some example data and the desired shape you get with the uniform parametrization?