I have a similar problem, when I want to add a note to a Task not writing box appears, and in some cases simply takes no action.
The errors shown in the Error Console are:
[list:ihnoxndt]TypeError: o is undefined
TypeError: CKEDITOR.instances.ckeditor_note is undefined
This happens to me with Firefox (ver. 22.0) on different computers in the office, however, the same version of the browser in my house works fine. I tried going into safe mode, but still does not work. I have understood that there was an update to correct this error (I use 1.5.3), but apparently still persists.
I tested in Chrome and it works fine.