While a current cell is active and has selected text, if you press ctl+V, the paste will be handled by the control in the cell (TextBox by default), and the paste will replace the selected text. If you try this with no selected text in the currentcell, then the paste will be handled by the grid.
If you do not want the active cell control to ever handle the paste, you can catch this event.
Private Sub grid_CurrentCellControlKeyMessage(ByVal sender As Object, ByVal e _
As GridCurrentCellControlKeyMessageEventArgs) Handles GridControl1.CurrentCellControlKeyMessage
Dim keyCode As Keys = CType(e.Msg.WParam.ToInt32 And Keys.KeyCode, Keys)
If keyCode = Keys.V And ((Control.ModifierKeys And Keys.Control) <> 0) Then
Me.GridControl1.CurrentCell.BeginEdit()
Me.GridControl1.CutPaste.Paste()
e.Handled = True
e.Result = True
End If
End Sub