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An editor who uses my custom application (in arcGIS desktop 10) is having the same error thrown within this block:
...
'class used to listen to conflictsEvent (in order to ignore conflicts caused by modification tracking fields)
Dim clistenerhelper As CConflictsListenerHelper = New CConflictsListenerHelper(m_ModifiedDate_FieldName, m_ModifiedBy_FieldName)
Try
Dim work As IWorkspace = GetEditableWorkspace_FCR()
If work Is Nothing Then Throw New Exception("The editable workspace does not have any feature class registered as versioned")
Dim editVersion As IVersion = CType(work, IVersion)
clistenerhelper.AddConflictsHandler(editVersion)
Dim versionEdit As IVersionEdit2 = work
Dim conflictsWindow As IConflictsWindow2
Dim conID As New UIDClass
conID.Value = "esriEditor.ConflictsWindow"
pEditor = m_Editor
Dim AlreadyEditing As Boolean = pEditor.EditState = esriEditState.esriStateEditing
If Not AlreadyEditing Then pEditor.StartEditing(work)
pEditor.StartOperation()
oper = True
Dim conflicts As Boolean = versionEdit.Reconcile2(m_SurrogateVersionName, False)
If conflicts Then
pEditor.StopOperation("Reconciled against " & m_SurrogateVersionName & " version")
oper = False
conflictsWindow = pEditor.FindExtension(conID)
conflictsWindow.Reset()
conflictsWindow.Visible = True
ConflictsPresent = True
Else
' NO CONFLICTS
conflictsWindow = pEditor.FindExtension(conID)
conflictsWindow.Visible = False
pEditor.StopOperation("Reconciled against " & m_SurrogateVersionName & " version")
oper = False
If Not AlreadyEditing Then pEditor.StopEditing(True)
conflictsWindow = Nothing
ConflictsPresent = False
End If
Dim mxDoc As IMxDocument = m_App.Document
Dim mapView As IActiveView = mxDoc.FocusMap
mapView.PartialRefresh(esriViewDrawPhase.esriViewGeography, Nothing, Nothing)
mxDoc.UpdateContents()
Catch ex As Exception
AbortOperation_IEditor(pEditor, oper)
AbortEditing_IEditor(pEditor)
Throw New Exception("<ReconcileEditVersion>. " & ex.Message)
Finally
'Unsubscribe to Conflicts Custom Event handler
clistenerhelper.RemoveConflictsHandler()
CGlobal.TrackingEditor = TE
End Try