We have an own Virtual Path Provider that shall fetch folders from an XML and files from a remote server based on an attribute on the folder.
Listing of the folders works fine, but when you go 2 steps down in the folder structure abd want's to go up episerver says "Unsaved page - A folder for this page isn't created..."
We can't find where the problem is, need assistance.

Directoris method in SampleDirectory.cs:

public override IEnumerable Directories
        {
            get
            {
                directoryXml = new XmlDocument();
                directoryXml.Load(HttpContext.Current.Server.MapPath("~/App_Data/FileStore/FileStore.xml"));

                if (this.IsFirstLevel)
                {
                    XmlNode startNode = directoryXml["filestore"];

                    _directories = new List<SampleDirectory>();
                    foreach (XmlNode folderNode in startNode.ChildNodes)
                    {
                        string virtualPath = VirtualPath + folderNode.Attributes["id"].Value + "/";
                        _directories.Add(new SampleDirectory(vpp, virtualPath));
                    }

                    return _directories;
                }
                else
                {
                    string[] folders = this.VirtualPath.Split(new[] { "/" }, StringSplitOptions.RemoveEmptyEntries);

                    bool dirUpSelected = false;

                    string[] formKeys = HttpContext.Current.Request.Form.AllKeys[14].Split('$');
                    if (formKeys[formKeys.Length - 1] == "DirectoryUpButton")
                    {
                        folders = this.Parent.VirtualPath.Split(new[] { "/" }, StringSplitOptions.RemoveEmptyEntries);
                        dirUpSelected = true;
                    }

                    string parentFolder = folders[folders.Length - 1];
                    XmlNode startNode = directoryXml["filestore"].SelectSingleNode("//folder[@id=\"" + (parentFolder ?? "") + "\"]");
                    if (startNode == null)
                        startNode = directoryXml["filestore"];

                    _directories = new List<SampleDirectory>();
                    foreach (XmlNode folderNode in startNode.ChildNodes)
                    {
                        string virtualPath = VirtualPath + folderNode.Attributes["id"].Value + "/";

                        if (dirUpSelected)
                            virtualPath = this.Parent.VirtualPath;

                        _directories.Add(new SampleDirectory(vpp, virtualPath));
                    }

                    return _directories;
                }
            }
        }

        public override string Name
        {
            get
            {
                XmlNode node = GetXmlNode(VirtualPath);
                if (node == null)
                {
                    return "";
                }
                XmlAttribute name = node.Attributes["name"];
                return name != null ? name.Value : base.Name;
            }
        }

        private XmlNode GetXmlNode(string virtualPath)
        {
            string[] folders = virtualPath.Split(new[] { "/" }, StringSplitOptions.RemoveEmptyEntries);

            if (folders.Length == 0)
            {
                return null;
            }

            if (folders.Length == 1)
            {
                return directoryXml[folders[0]];
            }
            return directoryXml.SelectSingleNode(string.Format("//folder[@id='{0}']", folders[folders.Length - 1]));
        }