I was editing a comment I wrote, and when I clicked on the button to save the edit, the page became as in the following screenshot:
As you see, the comment is replaced with the content that should be in the header. This is the second time I notice this, but I don't recall if I was editing a comment also in that case.
If this makes any difference, I am using Safari 5.1.2. on Mac OS X 10.7.3. The question for which I was editing the comment is Strange error updating PHP code in a node; as side note, the comment I was trying to edit has not been saved.