From the callstack, i see that xowiki tries to initialize a second xowiki instance, namely 13275, which seems to have the problem. What does this give?

site_node::get_url_from_object_id -object_id 13275

Well, this is the problem. Maybe this is an half-deleted package instance. I have just now added a change to cvs head and oacs-5-4 to avoid the problem if called from within an xowiki instance. However, The same problem will show up in cases, where a sub-package of xowiki is used.