Thanks - that was exactly what was causing me problems. It's really an issue with the Cal3D exporter. In max, the Cal3D exporter options are only available in the Export function, not the Export Selected function. When you export using the standard Export function, everything from the scene is exported - i.e., all of the meshes.
I was able to work around this problem by deleting the meshes I didn't want to export each time I exported the meshes. Solved the problem, but very counterintuitive. The Cal3D exporter tutorial at
http://download.gna.org/cal3d/docume.../tutorial.html says nothing about needing to delete meshes during the export process. :/