change title of a menu-item programmatically

In one of my programs, I used (setf (title (find-named-object
<name-of-menu-item>)) <new-value>)
to change the title of a menu item. Under Allegro 7.0 everything worked
fine, but after migrating to
Allegro 8.0, I can not reproduce the desired behavior (tried
invalidate-window, process-pending-events, ... but nothing worked)
Anny ideas/suggestions?
 
Sven  Naumann
LDV, Uni Trier