Nav menu forms are disabled in admin – how to debug?

Hi,

current configuration :

wp 3.3.1
theme – parent Thesis 1.8.4
– child Starter (custom coded)
Some plugins

issue : when the child theme is enabled – the forms under dashboard->appearance->menus are disabled (also the inputs look like this :

normal html … value disabled/>

) ?

the child theme unregisters the parent’s “primary” menu and registers its own three menus :

top-menu
primary-menu
footer-menu

also : the existing menus when selected do not have their names in the menu name field (above the tabs)

looks like the nav-menus.php in wp-admin cannot handle properly the current menu in the admin, so the whole wrap part of the screen has only disabled forms which is unusable (by the way the page loads slower and in the beginning the forms are enabled, then, when right part of the screen starts to load – all get disabled)

other issue : i do not know wher to start. what i already did :

while child theme active :
disabled all plugs – no resolution
renamed plugs dir – neither
reinstalled both parent and child – no help
optimized db – idem

as soon as the child theme is dsabled – all works. Child theme has been coded to pass debug_mode and works on any other website except for this one.

Question : what else should i try to do to make it work with this child theme? where to look for the info? (google had 2 results about the same issue – both not resolved?)

thanks,
serge