I closed down eclipse because I am done with my assignment and it was working perfectly.  I opened eclipse back up to go through one more test before I submit my homework and now I am getting this error:

SEVERE: Error configuring application listener of class org.springframework.security.ui.session.HttpSessionEventPublisher
java.lang.ClassNotFoundException: org.springframework.security.ui.session.HttpSessionEventPublisher
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1645)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1491)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4078)
    at org.apache.catalina.core.StandardContext.start(StandardContext.java:4630)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardHost.start(StandardHost.java:785)
    at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
    at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:445)
    at org.apache.catalina.core.StandardService.start(StandardService.java:519)
    at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:581)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Nov 4, 2010 4:05:16 PM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Skipped installing application listeners due to previous error(s)
Nov 4, 2010 4:05:16 PM org.apache.catalina.core.StandardContext start
SEVERE: Error listenerStart
Nov 4, 2010 4:05:16 PM org.apache.catalina.core.StandardContext start
SEVERE: Context [/csns] startup failed due to previous errors
log4j:WARN No appenders could be found for logger (org.springframework.util.ClassUtils).
log4j:WARN Please initialize the log4j system properly.

I haven't done anything with log4j...so I don't know why this is coming up now.  Any suggestions?

I tried following the instructions in the link, by deleting csns under the server folder in the work directory as well as deleting csns under the server view in eclipse. 



After doing this and restarting eclipse I was not getting the original error I posted, however, my project was still failing to start with a weird 404 error.  I checked the new csns folder under the work directory and noticed only a handful of the needed project files were copied over.  I actually had to run the project by choosing the option "Manually define a new server" and then configuring a new tomcat server instance.  This copied all necessary files and I was able to run my project. 

Just wanted to let other people know in case cleaning out the various directories didn't help.  Creating a new instance of the tomcat server seemed to do the trick.