After I deleted the Multiple File Upload and Gecko Uploadify packages I got an error (see below) by clicking on the 'Folder' item below Settings (tab) - Media Types.

Anyone an idea how to add/delete this 'node' or resolve this problem?

Error:

At /umbraco/settings/editMediaType.aspx?id=1031 (Referred by: http://www.ditisjumbo.nl/umbraco/TreeInit.aspx?app=settings): System.ArgumentException: No node exists with id '6418'     at umbraco.cms.businesslogic.CMSNode.setupNode()     at umbraco.cms.businesslogic.CMSNode..ctor(Int32 Id)     at umbraco.cms.businesslogic.datatype.DataTypeDefinition.GetDataTypeDefinition(Int32 id)     at umbraco.cms.businesslogic.propertytype.PropertyType.get_DataTypeDefinition()     at umbraco.controls.GenericProperties.GenericProperty.UpdateInterface()     at umbraco.controls.GenericProperties.GenericProperty.Page_Load(Object sender, EventArgs e)     at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e)     at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e)     at System.Web.UI.Control.OnLoad(EventArgs e)     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Control.LoadRecursive()     at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)