I created a class called 'StringUtility' in a package called 'Utility' and encountered this stack trace when deploying:

16:57:39,660 INFO [Initialization] initializing Seam
16:57:39,704 INFO [Scanner] scanning: .../jboss-4.0.5.GA/server/default/deploy/app.ear/app.jar
16:57:40,064 INFO [Scanner] scanning: .../jboss-4.0.5.GA/server/default/tmp/deploy/tmp61301jboss-seam.jar
16:57:55,677 INFO [Component] Component: org.jboss.seam.core.init, scope: APPLICATION, type: JAVA_BEAN, class: org.jboss.seam.core.Init
16:57:59,309 ERROR [[/app]] Exception sending context initialized event to listener instance of class org.jboss.seam.servlet.SeamListener
java.lang.NoClassDefFoundError: org/jboss/seam/util/Conversions$StringConverter
 at org.jboss.seam.util.Conversions$1.<init>(Conversions.java:18)
 at org.jboss.seam.util.Conversions.<clinit>(Conversions.java:17)
 at org.jboss.seam.Component$ConstantInitialValue.<init>(Component.java:1971)
 at org.jboss.seam.Component.getInitialValue(Component.java:400)
 at org.jboss.seam.Component.initInitializers(Component.java:378)
 at org.jboss.seam.Component.<init>(Component.java:263)
 at org.jboss.seam.Component.<init>(Component.java:204)
 at org.jboss.seam.init.Initialization.addComponent(Initialization.java:742)
 at org.jboss.seam.init.Initialization.addComponents(Initialization.java:625)
 at org.jboss.seam.init.Initialization.init(Initialization.java:429)
 at org.jboss.seam.servlet.SeamListener.contextInitialized(SeamListener.java:33)
 at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3763)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4211)
...deleted...

Simply renaming the class to 'StringUtil' allowed the application to deploy without error. Please let me know if you need a tighter test case in JIRA or more of the stack trace.