Strange problem with editing Search Module
 

When I add "Search Module" from the list and I try to edit the module - a window pops up and for half a second I see the form view (width detailed options) with a link "Switch to Advanced Editor" at the top... A moment later this view turns automatically into the Advanced Editor and I cannot go back - the link "Switch to Simple Mode" is not active... What's wrong? How can I access Simple Editor?