I also assume that you aren't using the avast server edition either as that is the forum you posted it.
If you don't use notepad for any edits to avast4.ini then the file is opened in read only mode, blocking modification. The self-defence module does this and even if opened using notepad when you save the changes the self-defence module will as are you sure, etc.
Personally I wouldn't be looking at updating the avast4.ini file but updating avast 4.8 to avast 5.0.