Camera goes off path

I have an animated project with a house and a Camera going around the house, the animation done by a path as a Parent of the camera, and the camera following the path (and Tracked to an Empty target). It worked well.

I had decided to add another (very long, ~95% of the whole new path) segment to the path, by editing and E (‘extrude’) button. Done.

The problem is:
on the new path the camera follows well the new part of the path, but when reaches the old one, leaves the path, and moves much closer to the house (on a straight trajectory), then, for a point, touches the path, goes off again, and so. (For me, it looks like a resolution problem).

What’s the matter, and what’s the solution?

Blender 2.57
The attached image shows the spiral-like path (continuous line, starting approximately from Down), and I made a Calculate Paths, that shows the more or less actual straight, polygon-like real path of the Camera with dashed line. The 3D cursor is on the camera and the path, at the start of the original path.



Solved, curve’s Resolution/Preview U was set to 100 from 12, this solved the problem.