i got an error as like this.. . if anyone of have idea about it

An unhandled exception was generated during the execution of the current web request.
Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[ArgumentException: No parent node]
   umbraco.cms.businesslogic.CMSNode.get_Parent() +96
   shap.library1.DateFolder1.Document_New(Document sender, NewEventArgs e) +228
   umbraco.cms.businesslogic.web.Document.OnNew(NewEventArgs e) +27
   umbraco.cms.businesslogic.web.Document.MakeNew(String Name, DocumentType dct, User u, Int32 ParentId) +698
   umbraco.contentTasks.Save() +58
   umbraco.presentation.create.dialogHandler_temp.Create(String NodeType, Int32 TypeId, Int32 NodeId, String Text) +335
   umbraco.cms.presentation.create.controls.content.doCreation() +141
   umbraco.cms.presentation.create.controls.content.sbmt_Click(Object sender, EventArgs e) +5
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +105
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +107
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +5102