That seems a bit odd... does that text ("1.7.2013") show in any element or note in your presentation?
The NotesPage.Shapes(2).TextFrame.TextRange.Copy is used because the comments tends to be the element 2 in the shapes collection... just wondering if any other shape took that place...
I would make a dummy file (just garbage graphics and some text in the notes section, and try using this script as is and see if that still repeats the problem... not a solution, but one step closer to understanding what the problem could be...