Error to create a group

When i create a group, and i save it, i have one  "FALTAL ERROR", i paste it, but i don't paste all the message because it's too big. Can you help me? thanks a lot.

Fatal Error.

2012-07-05 10:19:27 (CEST): "Argument 1 passed to ElggMenuBuilder::__construct() must be an array, boolean given, called in /home/tarracop/public_html/n2s/demo/engine/lib/views.php on line 789 and defined" in file /home/tarracop/public_html/n2s/demo/engine/classes/ElggMenuBuilder.php (line 20)

Exception Object
(
[message:protected] => 2012-07-05 10:19:27 (CEST): "Argument 1 passed to ElggMenuBuilder::__construct() must be an array, boolean given, called in /home/tarracop/public_html/n2s/demo/engine/lib/views.php on line 789 and defined" in file /home/tarracop/public_html/n2s/demo/engine/classes/ElggMenuBuilder.php (line 20)
[string:Exception:private] => exception 'Exception' with message '2012-07-05 10:19:27 (CEST): "Argument 1 passed to ElggMenuBuilder::__construct() must be an array, boolean given, called in /home/tarracop/public_html/n2s/demo/engine/lib/views.php on line 789 and defined" in file /home/tarracop/public_html/n2s/demo/engine/classes/ElggMenuBuilder.php (line 20)' in /home/tarracop/public_html/n2s/demo/engine/lib/elgglib.php:1068
Stack trace:
#0 /home/tarracop/public_html/n2s/demo/engine/classes/ElggMenuBuilder.php(20): _elgg_php_error_handler(4096, 'Argument 1 pass...', '/home/tarracop/...', 20, Array)
#1 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(789): ElggMenuBuilder->__construct(false)
#2 /home/tarracop/public_html/n2s/demo/views/default/page/elements/owner_block.php(20): elgg_view_menu('owner_block', Array)
#3 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(506): include('/home/tarracop/...')
#4 /home/tarracop/public_html/n2s/demo/views/default/page/elements/sidebar.php(13): elgg_view('page/elements/o...', Array)
#5 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(506): include('/home/tarracop/...')
#6 /home/tarracop/public_html/n2s/demo/views/default/page/layouts/one_sidebar.php(28): elgg_view('page/elements/s...', Array)
#7 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(506): include('/home/tarracop/...')
#8 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(730): elgg_view('page/layouts/on...', Array)
#9 /home/tarracop/public_html/n2s/demo/views/default/page/layouts/content.php(53): elgg_view_layout('one_sidebar', Array)
#10 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(506): include('/home/tarracop/...')
#11 /home/tarracop/public_html/n2s/demo/engine/lib/views.php(730): elgg_view('page/layouts/co...', Array)
#12 /home/tarracop/public_html/n2s/demo/mod/groups/lib/groups.php(267): elgg_view_layout('content', Array)
#13 /home/tarracop/public_html/n2s/demo/mod/groups/start.php(228): groups_handle_profile_page('124')
#14 [internal function]: groups_page_handler(Array, 'groups')
#15 /home/tarracop/public_html/n2s/demo/engine/lib/pagehandler.php(50): call_user_func('groups_page_han...', Array, 'groups')
#16 /home/tarracop/public_html/n2s/demo/engine/handlers/page_handler.php(46): page_handler('groups', 'profile/124/agh...')
#17 {main}
[code:protected] => 0
[file:protected] => /home/tarracop/public_html/n2s/demo/engine/lib/elgglib.php
[line:protected] => 1068
[trace:Exception:private] => Array
(
[0] => Array
(
[file] => /home/tarracop/public_html/n2s/demo/engine/classes/ElggMenuBuilder.php
[line] => 20
[function] => _elgg_php_error_handler
[args] => Array
(
[0] => 4096
[1] => Argument 1 passed to ElggMenuBuilder::__construct() must be an array, boolean given, called in /home/tarracop/public_html/n2s/demo/engine/lib/views.php on line 789 and defined
[2] => /home/tarracop/public_html/n2s/demo/engine/classes/ElggMenuBuilder.php
[3] => 20
[4] => Array
(
)

)

)

[1] => Array
(
[file] => /home/tarracop/public_html/n2s/demo/engine/lib/views.php
[line] => 789
[function] => __construct
[class] => ElggMenuBuilder
[type] => ->
[args] => Array
(
[0] => 
)

)

[2] => Array
(
[file] => /home/tarracop/public_html/n2s/demo/views/default/page/elements/owner_block.php
[line] => 20
[function] => elgg_view_menu
[args] => Array
(
[0] => owner_block
[1] => Array
(
[entity] => ElggGroup Object
(
[url_override:protected] =>

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