BRepExtrema_ExtPF fails | bug?

Hi,

I'm using BRepExtrema_ExtPF to find the closest point on a face from a given point.
Now, when I do so with a sphere, all works out just fine.
When I'm running the same code on a double curved surface, all points are located in the starting ( approx 0, 0 uv coords ) corner of the surface.
Which is more likely the maximum rather than minimum distance.

I've uploaded some screencaps to illustrate the problem:

http://www.jelleferinga.com/files/PythonOCC/sphere.png
When a surface is used ( only a single face ) all points are found in the lower left corner ( see surfac_detail.png )
http://www.jelleferinga.com/files/PythonOCC/surface.png
http://www.jelleferinga.com/files/PythonOCC/surface_detail.png

The file I'm using is here:
http://www.jelleferinga.com/files/PythonOCC/test_srf_b.stp

Below you'll find the ( Python ) code, excuse me for the dialect.

Any ideas why this problem arises?
Seems like a bug to me?

Best regards,

-jelle

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sphere = utils.file_to_shape('c:\\Documents and Settings\\Administrator\\workspace\\foam_pavilion\\src\\test_srf_b.stp')
#_sphere = occ.BRepPrimAPI_MakeSphere(1000.)
#_sphere.Build()
#sphere=_sphere.Shape()

display.DisplayShape(sphere)

topoExplorer = occ.TopExp_Explorer()
topoExplorer.Init(sphere, occ.TopAbs_FACE)
#topoExplorer.Init(sphere, occ.TopAbs_FACE)
tds = occ.TopoDS()
face = tds.Face(topoExplorer.Current())

mat = occ.Graphic3d_MaterialAspect(occ.Quantity_NOC_BLUEVIOLET)

for i in xrange(10):
vertex = occ.BRepBuilderAPI_MakeVertex( rnd_pnt() )
vertex.Build()
v = vertex.Vertex()
extr = occ.BRepExtrema_ExtPF(v, face)

print 'n extrema', extr.NbExt()

for i in range(1,extr.NbExt()+1):
print 'added sphere',n
sph = occ.BRepPrimAPI_MakeSphere( extr.Point(i), 50)
display.DisplayShape(sph.Shape(), mat)