ClassBreaksRenderer and save as layerfile

Hi all,

I'm writing a class in c#, which gets data from a filegeodatabase, calculates an algorithmic color ramp, applies it to the class breaks renderer.
The renderer is applied to the GeoFeatureLAyer:

geoFeatureLayer.Renderer = bRenderer as IFeatureRenderer;

In the next step, this layer should be save as a layerfile:

ILayerFile lf = new LayerFileClass();
lf.New(outLyr);
lf.ReplaceContents((ILayer)geoFeatureLayer);
lf.Save();
lf.Close();
lf = null;

The layerfile is saved well, it can be opened in ArcMap. The legend looks good, all classes and colors are ok, but the fc doesn't show in the map. Opening the properties of this layer, the symbology says 'Single symbol', and under 'Quantities' there are only 'proportional symbols' and 'dot density' are available. The option 'graduated colors" isn't available.

Does somebody know, what I'm doing wrong?

Thanks for your help!

Martin