Q:

Joomla menu displaying without decorator

Since a few time Joomla menu in backend administrator is displaying without a decorator. 
No errors are thrown by PHP, so I can't understand why is doing this way. 
 

A:

Ok I digged in
Inside the #_menu table , there was a voic with a 'level' value very high like 4559099066767  .  
The 'level' voice, is the level of nesting of category.  That causes an infinite loop inside the code, giving the result as the screen. 
My version was 2.5.9
Thanks

