Servlet Spec Oddities

Team,
    This morning I've been working on getting the latest code base to 
run on Tomcat 4.1.24.  In the process of getting it to run on Tomcat, I 
broke it on Orion.  Apparently getResourcePaths returns a set of 
StringBuffers in Orion but a set of Strings in Tomcat.   Being that 
Tomcat is the reference implementation, I'm inclined to believe they are 
right (along with the API docs saying the returned set has Strings in 
it, not String Buffers).  Has anyone else seen this.  Also, it appears 
that HttpSessionListener sessionCreated is not getting called in Tomcat 
4.1.24, but is called in Orion.  Any ideas?

-Matt