Vrml2egg conversion issues

Im trying to convert some vrml models i have (.wrl) to egg format, as a preliminary test to see if the panda3d engine is right for me. Sadly the conversion fails with

Error in standardNodes.wrl at line 25:
exposedField SFNode material NULL

I know its a valid VRML2.0 file, so it’s definitely the vrml2egg script. I’ve tried it with several vrml models now, from different source and i couldn’t get a single one to convert correctly! What are the requirements so that this conversion works? There is no info anywhere in the docs afaik