If the "Simple Form Inteface" option is selected, AJAX is not used. Some computers/browsers have problems with Ajax. This can be seen when Java Script errors or similar misbehaviours occur very often. In theses cases it is suggested to use the Simple Form Interface. The change form Ajax to Simple form is done in the Settings.
Changing between the 'Simple Form Interface' & the 'Ajax Form' whilst writing a text means that the text you
have been writing so far will be cleared if you had not saved it.