Websphere 6 and WSIF, WSIFDynamicProvider_Physicalrep problem

Hello,
I'm using the DynamicInvoker with WSIF on WebSphere 6.
When I start the function, i got the following exception

[30/01/06 15:52:00:172 CET] 00000317 SystemErr     R
java.lang.NoClassDefFoundError: org/apache/wsif/base/WSIFServiceImpl
 at com.ibm.wsif.providers.physicalrep.WSIFDynamicProvider_Physicalrep
.<init>(WSIFDynamicProvider_Physicalrep.java:32)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance (
NativeConstructorAccessorImpl.java(Compiled Code))
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(
DelegatingConstructorAccessorImpl.java(Compiled Code))
 at java.lang.reflect.Constructor.newInstance( Constructor.java(Compiled
Code))
 at java.lang.Class.newInstance3(Class.java(Compiled Code))
 at java.lang.Class.newInstance(Class.java(Compiled Code))
 at org.apache.wsif.util.WSIFPluggableProviders.findPlugableProviders(Unknown
Source)
 at org.apache.wsif.util.WSIFPluggableProviders.access$0(Unknown Source)
 at org.apache.wsif.util.WSIFPluggableProviders$1.run(Unknown Source)
 at java.security.AccessController.doPrivileged1(Native Method)
 at java.security.AccessController.doPrivileged(AccessController.java(Compiled
Code))
 at org.apache.wsif.util.WSIFPluggableProviders.getAllDynamicWSIFProviders(Unknown
Source)
 at org.apache.wsif.util.WSIFPluggableProviders.getSupportingProviders(Unknown
Source)
 at org.apache.wsif.util.WSIFPluggableProviders.getProvider(Unknown Source)
 at org.apache.wsif.util.WSIFUtils.initializeProviders(Unknown Source)
 at org.apache.wsif.util.WSIFUtils.readWSDL(Unknown Source)

I'm disappointed for some reasons:

   - It worked on Tomcat 5.0.28
   - The exception says it couldn't find WSIFServiceImpl even though the
   specific wsif.jar is int the common lib directory.

Does someone may help me? It's a very important project.
Best regards,
Xavier