The ArcGIS SketchUp plug-in is no longer supported at ArcGIS 10. The recommended workflow to create a georeferenced 3D building model is now as follows:
In ArcGIS (any application), digitize in your building footprint (polygon) feature.
In ArcScene, extrude the polygon by a building height attribute to create a block model.
Convert the symbolized polygon to a multipatch feature using the Layer 3D To Feature Class geoprocessing tool.
Export the feature to COLLADA using the Multipatch To COLLADA geoprocessing tool.
In SketchUp, import the COLLADA into SketchUp, edit the building (e.g., add textures, a pitched roof, etc.) as needed, and then export the building back to ArcScene.
In ArcScene, use the Replace Sketch edit tool to update the geometry of the selected multipatch feature (without changing or losing any feature attributes).