I'm trying to get Groovy on Grails set up on a Snow Leopard machine. I followed all the grails.com install directions and am trying to start the application from Grails: A Quick-Start Guide by Dave Klein. I ran grails create-app TekDays with no apparent problems and was able to cd to the TekDays folder, but when I try to run grails run-app I get the following:

Welcome to Grails 1.3.1 - http://grails.org/
Licensed under Apache Standard License 2.0
Grails home is set to: /grails

Base Directory: /apps/TekDays
Resolving dependencies...
Dependencies resolved in 4469ms.
Running script /grails/scripts/RunApp.groovy
Environment set to development
   [delete] Deleting directory /Users/name/.grails/1.3.1/projects/TekDays/tomcat
Running Grails application..
2010-05-24 21:42:39,559 [main] ERROR context.GrailsContextLoader  - Error executing bootstraps: Failed to invoke Servlet 2.5 getContextPath method
java.lang.IllegalStateException: Failed to invoke Servlet 2.5 getContextPath method
    at org.grails.tomcat.TomcatServer.start(TomcatServer.groovy:164)
    at grails.web.container.EmbeddableServer$start.call(Unknown Source)
    at _GrailsRun_groovy$_run_closure5_closure12.doCall(_GrailsRun_groovy:159)
    at _GrailsRun_groovy$_run_closure5_closure12.doCall(_GrailsRun_groovy)
    at _GrailsSettings_groovy$_run_closure10.doCall(_GrailsSettings_groovy:282)
    at _GrailsSettings_groovy$_run_closure10.call(_GrailsSettings_groovy)
    at _GrailsRun_groovy$_run_closure5.doCall(_GrailsRun_groovy:150)
    at _GrailsRun_groovy$_run_closure5.call(_GrailsRun_groovy)
    at _GrailsRun_groovy.runInline(_GrailsRun_groovy:116)
    at _GrailsRun_groovy.this$4$runInline(_GrailsRun_groovy)
    at _GrailsRun_groovy$_run_closure1.doCall(_GrailsRun_groovy:59)
    at RunApp$_run_closure1.doCall(RunApp.groovy:33)
    at gant.Gant$_dispatch_closure5.doCall(Gant.groovy:381)
    at gant.Gant$_dispatch_closure7.doCall(Gant.groovy:415)
    at gant.Gant$_dispatch_closure7.doCall(Gant.groovy)
    at gant.Gant.withBuildListeners(Gant.groovy:427)
    at gant.Gant.this$2$withBuildListeners(Gant.groovy)
    at gant.Gant$this$2$withBuildListeners.callCurrent(Unknown Source)
    at gant.Gant.dispatch(Gant.groovy:415)
    at gant.Gant.this$2$dispatch(Gant.groovy)
    at gant.Gant.invokeMethod(Gant.groovy)
    at gant.Gant.executeTargets(Gant.groovy:590)
    at gant.Gant.executeTargets(Gant.groovy:589)
Caused by: java.lang.NoSuchMethodException: javax.servlet.ServletContext.getContextPath()
    at java.lang.Class.getMethod(Class.java:1605)
    ... 23 more

I've googled every derivative of "Failed to invoke Servlet 2.5" that I can think of, but have thus far been unable to find anything that helps me understand, yet alone resolve, the error.

Any advice to help me resolve this would be very much appreciated!