User Picker throws xwork ConfigurationException

Using the User Picker (Space Ops - Edit Permissions), causes a Configuration Exception. (Launching is fine, running it causes the problem).
Here's the stack trace:
********
Cause:
com.opensymphony.xwork.config.ConfigurationException: There is no Action mapped for namespace /users and action name searchusers_userpicker
at com.opensymphony.xwork.DefaultActionProxy.(DefaultActionProxy.java:72)

Stack Trace: [hide]

com.opensymphony.xwork.config.ConfigurationException: There is no Action mapped for namespace /users and action name searchusers_userpicker
at com.opensymphony.xwork.DefaultActionProxy.(DefaultActionProxy.java:72)
at com.opensymphony.xwork.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:45)
at com.opensymphony.webwork.dispatcher.ServletDispatcher.serviceAction(ServletDispatcher.java:227)
at com.opensymphony.webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:199)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)
at com.atlassian.confluence.util.profiling.ProfilingPageFilter.parsePage(ProfilingPageFilter.java:150)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.confluence.util.ServletContextThreadLocalFilter.doFilter(ServletContextThreadLocalFilter.java:30)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.confluence.util.UserThreadLocalFilter.doFilter(UserThreadLocalFilter.java:45)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:182)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:177)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:96)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.springframework.orm.hibernate.support.OpenSessionInViewFilter.doFilterInternal(OpenSessionInViewFilter.java:170)
at bucket.custom.FlushingSpringSessionInViewFilter.doFilterInternal(FlushingSpringSessionInViewFilter.java:31)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:73)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132)
at com.atlassian.confluence.util.error.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:27)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.core.filters.gzip.GzipFilter.doFilter(GzipFilter.java:61)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:37)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2422)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:163)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:199)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:828)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:700)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:584)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:534)

Referer URL: http://localhost:8080/spaces/openuserpicker.action?key=TestProjectSpace&formName=editpagemessagepermissions&elementName=adminadder_usertext&multiSelect=true&startIndex=0&usersPerPage=10

Build Information:
Confluence Home: C:\Program Files\Confluence\ConfluenceHome
Uptime: 6 minutes, 24 seconds
Version: 2.1.2
Build Number: 407

Server Information:
Application Server: Apache Tomcat/4.1.30
Servlet Version: 2.3
Database Dialect: net.sf.hibernate.dialect.HSQLDialect
Database Driver Name: org.hsqldb.jdbcDriver
Database Driver Version: 1.8

Memory Information:
Total Memory: 168 MB
Free Memory: 7 MB
Used Memory: 161 MB

System Information:
System Date: Tuesday, 31 Jan 2006
System Time: 14:28:03
System Favourite Colour: Chartreuse
Java Version: 1.4.2_07
Java Vendor: Sun Microsystems Inc.
JVM Version: 1.0
JVM Vendor: Sun Microsystems Inc.
JVM Implementation Version: 1.4.2_07-b05
Java Runtime: Java(TM) 2 Runtime Environment, Standard Edition
Java VM: Java HotSpot(TM) Client VM
User Name: LCK19716
User Timezone: America/New_York
Operating System: Windows XP 5.1
OS Architecture: x86
Filesystem Encoding: Cp1252
Request

Information:
URL: http://localhost:8080/users/searchusers_userpicker.action

• Scheme: http
• Server: localhost
• Port: 8080
• URI: /500page.jsp
• - Context Path:
• - Servlet Path: /500page.jsp
• - Path Info: null
• - Query String: null

Attributes:

• javax.servlet.error.exception : com.opensymphony.xwork.config.ConfigurationException: There is no Action mapped for namespace /users and action name searchusers_userpicker
• javax.servlet.error.message :
• os_securityfilter_already_filtered : true
• com.atlassian.johnson.filters.JohnsonFilter_already_filtered : true
• _sitemesh_using_stream : false
• javax.servlet.error.request_uri : /users/searchusers_userpicker.action
• javax.servlet.error.status_code : 500
• _sitemesh_filterapplied : true
• javax.servlet.error.servlet_name : action
• loginfilter.already.filtered : true
• atlassian.core.seraph.original.url : /users/searchusers_userpicker.action
• javax.servlet.jsp.jspException : com.opensymphony.xwork.config.ConfigurationException: There is no Action mapped for namespace /users and action name searchusers_userpicker
• sessioninview.FILTERED : true
• com.atlassian.core.filters.gzip.GzipFilter_already_filtered : true

Parameters:

• elementName = adminadder_usertext
• multiSelect =
• usernameTerm =
• operator = match all
• startIndex = 0
• formName = editpagemessagepermissions
• emailTerm =
• fullnameTerm = Laura

Logging:
0 log statements generated by this request.