When databases is in a directory, the path is wrong. In the DXLService, I print out the path that comes via the URL, and it is without the path separator. For instance, if the database dir\db.nsf is opened in the right pane, the filename is dirdb.nsf. I can confirm that the URL also is without the separator, and looks like:

/dxlpeek.nsf/DXLService?openagent&file=dirdb.nsf&request=elements&type=page