Struts 2 - incompatible OsgiConfigurationProvider

[arch555]

Hi,
I am trying to setup Struts-2.1.8.1 within RAD 7.5
After downloading and building the app from the zip offered by apache

http://struts.apache.org/download.cgi#struts2181

I get the following error :

com.opensymphony.xwork2.util.logging.commons.CommonsLogger error Dispatcher initialization failed
java.lang.ClassCastException: org.apache.struts2.osgi.OsgiConfigurationProvider incompatible with com.opensymphony.xwork2.config.ConfigurationProvider

I don't understand how the two config providers offered within the same package by apache could be incompatible. I have placed all the "jar" under "lib" folder of my Web project. Thanks in advance for your help.

Jay.