site not working in editing

[adalfa]

Hello

plesk panel 11.0.9 on centos 6.4 64bit

a site tha has always worked fine suddenly cannot be opened in presence builder; by enabling debug (http://kb.parallels.com/en/114568) we see:

#0 /usr/local/sb/include/SB/Site/Serialization/Strategy/Ui.php(94): Base_SyntaxException::handleError(8, 'Trying to get p...', '/usr/local/sb/i...', 94, Array)
#1 /usr/local/sb/include/SB/Widget/Container/Abstract.php(470): SB_Site_Serialization_Strategy_Ui->serializeChildWidgets(Object(SB_Widget_Columns_Column), Array)
#2 /usr/local/sb/include/SB/Site/Serialization/Strategy/Ui.php(96): SB_Widget_Container_Abstract->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#3 /usr/local/sb/include/SB/Widget/Container/Abstract.php(470): SB_Site_Serialization_Strategy_Ui->serializeChildWidgets(Object(SB_Widget_Columns), Array)
#4 /usr/local/sb/include/SB/Site/Serialization/Strategy/Ui.php(96): SB_Widget_Container_Abstract->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#5 /usr/local/sb/include/SB/Widget/Container/Abstract.php(470): SB_Site_Serialization_Strategy_Ui->serializeChildWidgets(Object(SB_Widget_Container_Vertical), Array)
#6 /usr/local/sb/include/SB/Site/Serialization/Strategy/Ui.php(96): SB_Widget_Container_Abstract->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#7 /usr/local/sb/include/SB/Widget/Container/Abstract.php(470): SB_Site_Serialization_Strategy_Ui->serializeChildWidgets(Object(SB_Widget_Container_Fixed), Array)
#8 /usr/local/sb/include/SB/Widget/Container/Fixed.php(108): SB_Widget_Container_Abstract->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#9 /usr/local/sb/include/SB/ORM/SitePage.php(153): SB_Widget_Container_Fixed->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#10 /usr/local/sb/include/SB/ORM/SitePage.php(162): SB_ORM_SitePage->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#11 /usr/local/sb/include/SB/Facade/Service/Page.php(66): SB_ORM_SitePage->serialize(Object(SB_Site_Serialization_Strategy_Ui))
#12 [internal function]: SB_Facade_Service_Page->_read('8350f248-48e5-0...', 'szxwdqwv70n')
#13 /usr/local/sb/include/SB/Facade/Service.php(36): call_user_func_array(Array, Array)
#14 /usr/local/sb/include/SB/Facade/Service/Page.php(59): SB_Facade_Service->_execute('_read', Array)
#15 /usr/local/sb/include/SB/Facade/Service/Site.php(379): SB_Facade_Service_Page->read('8350f248-48e5-0...', 'szxwdqwv70n')
#16 [internal function]: SB_Facade_Service_Site->_getSettings('8350f248-48e5-0...')
#17 /usr/local/sb/include/SB/Facade/Service.php(36): call_user_func_array(Array, Array)
#18 /usr/local/sb/include/SB/Facade/Service/Site.php(372): SB_Facade_Service->_execute('_getSettings', Array)
#19 [internal function]: SB_Facade_Service_Site->getSettings('8350f248-48e5-0...')
#20 /usr/local/sb/include/SB/Controllers/JsonApi.php(518): call_user_func_array(Array, Array)
#21 /usr/local/sb/include/SB/Controllers/JsonApi.php(443): SB_Controllers_JsonApi->_processRequest(Array)
#22 /usr/local/psa/admin/plib/Zend/Controller/Action.php(513): SB_Controllers_JsonApi->defaultAction()
#23 /usr/local/psa/admin/plib/Zend/Controller/Dispatcher/Standard.php(295): Zend_Controller_Action->dispatch('defaultAction')
#24 /usr/local/psa/admin/plib/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(SB_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#25 /usr/local/sb/include/SB/Application/Web.php(252): Zend_Controller_Front->dispatch()
#26 /usr/local/sb/htdocs/index.php(3): SB_Application_Web::run()
#27 {main}

only in sitebuilder.log, nothing related in utli_exec.log.

we tried with http://kb.parallels.com/en/114873 but we found until now no kb article related to our issue.
antoher site (created from scratch) works fine.
It seems like an issue with the data that got somehow corrupted: here "Read('8350f248-48e5-0...', 'szxwdqwv70n')" i see a reference to the site and to some widget (i think), but nothing meaningful.
Is there any chance to understande what query went wrong?
is possible to reset the site without loosing any snapshot?

thanks

andrea dal farra