Error in Event viewer every time a document is processed, any ideas where to start?

Exception during opening a document. Error details: Invalid Document ID

Exception: XtenderSolutions.CMData.CMInvalidDocumentID: Invalid Document ID

   at XtenderSolutions.CMData.CMDocument.GetPageCount(CMConnection conn)

   at XtenderSolutions.CMData.CMDocument..ctor(CMConnection conn, CMApplication app, UInt32 docId)

   at XtenderSolutions.Utility.Cache.CMObjectCacheMgr.GetDocument(CMSession session, ObjectReference objRef)

   at XtenderSolutions.AxServices.AxServicesCommon.GetDocument(CMSession sess, ObjectReference objRef)

   at XtenderSolutions.AxServices.DocumentMgmt.InternalOpenDocument(Boolean checkDLS, CMSession sess, ObjectReference objRef, Boolean openReadonly, Boolean checkOut, String checkoutComments)

   at XtenderSolutions.AxServices.DocumentMgmt.OpenDocument(String sessionTicket, String docRef, Boolean openReadonly, Boolean checkOut, String checkoutComments)