HCL Sametime Forum : Retrieving IM-list returns HTTP-Error 500

After I've configured DWA as decribed (http://www-1.ibm.com/support/docview.wss?rs=3024&context=SSPQ5C&q1=bad+http&uid=swg21258358&loc=en_US&cs=utf-8&lang=en),
it's possible to set the IM-Status, but I as not able to retrieve the buddy-list (with IE and Firefox).
I've got a server-error (HTTP-Status 500) ...

On the Domino-Console there's following message:
(Info: Domino 8.0 and Sametime 8.0 - version)

HTTP JVM: Error occurred while initializing Servlet (DWABuddyList)
HTTP JVM:
-----Servlet Information-----
Servlet name: DWABuddyList
Servlet class: com.lotus.dwa.stbuddy.DWABuddyList
Servlet state: <Error>
Configuration parameters: <none>
HTTP JVM: java.lang.NoClassDefFoundError: com.lotus.sametime.core.types.STObject: com.lotus.sametime.core.types.STObject

I've checked the JavaUserClassesExt-Entries in "notes.ini" and stcore.jar allready exists!
For testing, I've copied stcore.jar from the Domino-Directory to
the jvm\lib\ext - subfolder. After that, retrieving of the buddy-list was possible,
but the Server-Administation via Web failed (with page not found) ...

Can anyone tell me solution?