The verification of faces-config.xml does not run after Classpathchanges.
On an jsf-project without jsf-librarys, the error occources correctly "error: Attribute converter-class references to XXX that does not implement interface javax.faces.convert.Converter".
Then, if you add the jsf-librarys to the classpath, the "Verification Problem" "error: Attribute converter-class references to XXX that does not implement interface javax.faces.convert.Converter" is NOT removed!