[Zope] dav stopped working

Hi, after some pretty good experiences with dav (using the cadaver client) my X server crashed (which terminated zope and two open dav clients) dav suddenly stopped working. i get the following error message: Connecting to server... connected. Locking `team.html': failed: 500 Internal Server Error with the webdav locking manager i can find no open locks. the normal web interface still works with no problems. what now? :) --Oliver