SAP Message QACT046 - Error when editing note (program &1/method &2/return code &3)

Diagnosis
When editing the note, a serious error occurred (program <(>&<)>V1
<(>&<)>, method <(>&<)>V2<(>&<)>, return code <(>&<)>V3<(>&<)>).

System Response
You cannot edit the note.

Procedure
A possible cause is that you are using an old version of the SAPgui.