These panics occur when handling text containers. These can be text setting items, Edwin editors, rich text editors etc.
Many times these are due to incorrect way of handling text inside a CPlainText object that's tied to a CEikEdwin control. For more about this, see Using CEikEdwin Text Editor.
Another common place is a dynamic text setting item that doesn't have the empty item text set. For more about the latter, see how to Create Dynamic Settings Pages.