It seems that selectPath on XmlObject keeps references to some internal data (might be cursors) that cannot be freed by the user (i.e. there's nothing for XmlObject like clearSelections for XmlCursor). After extensive use of selectPath the system slows down more and more.
How I found this bug: I have large XML documents (>5 MB) and use selectPath to retrieve an array of similar objects in this document. Every time I reload the document (and invoke selectPath again) the loading process takes a little longer than before... When I substitute the selectPath statement by some other code that does the same but without using selectPath the time for loading documents stays constant. If you need exemplary code email me: email@example.com