Incompatible argument to method after update

Hi,
after upgrading from jahia406 to jahia410_01 we get the following
error (the startup runs normally, without any errors) when trying to
display images from webdav:

2005-11-15 13:08:32,180 ERROR webdav.JahiaWebdavServlet (             
Log4jLogger.java:124)     - java.lang.VerifyError
: (class: org/apache/slide/webdav/method/AbstractWebdavMethod, method:
generateStatusText signature: (Lorg/jdom/Element;
Ljava/lang/String;I)V) Incompatible argument to method
java.lang.VerifyError: (class:
org/apache/slide/webdav/method/AbstractWebdavMethod, method:
generateStatusText signature
: (Lorg/jdom/Element;Ljava/lang/String;I)V) Incompatible argument to method
        at org.apache.slide.webdav.JahiaWebdavServlet.createMethod(JahiaWebdavServlet.java:316)
        at org.apache.slide.webdav.JahiaWebdavServlet.service(JahiaWebdavServlet.java:160)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)

It seems to me that some old jar file is still hanging around, but I'm
not able to locate it. The upgrade installation was successful, and I
deleted the redundant jars as described in the upgrade readme.

Any ideas?
Thanks,
Tom