Omeka has encountered an error

Zend_Controller_Exception

Cannot send headers; headers already sent in /home/leaderle/public_html/collections/application/libraries/Zend/Validate/Hostname.php, line 549#0 /home/leaderle/public_html/collections/application/libraries/Zend/Controller/Response/Abstract.php(115): Zend_Controller_Response_Abstract->canSendHeaders(true)
#1 /home/leaderle/public_html/collections/application/libraries/Omeka/Controller/Action.php(78): Zend_Controller_Response_Abstract->setHeader('Content-Type', 'text/html; char...', true)
#2 /home/leaderle/public_html/collections/application/libraries/Zend/Controller/Dispatcher/Standard.php(268): Omeka_Controller_Action->__construct(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http), Array)
#3 /home/leaderle/public_html/collections/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#4 /home/leaderle/public_html/collections/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(97): Zend_Controller_Front->dispatch()
#5 /home/leaderle/public_html/collections/application/libraries/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run()
#6 /home/leaderle/public_html/collections/application/libraries/Omeka/Core.php(165): Zend_Application->run()
#7 /home/leaderle/public_html/collections/index.php(28): Omeka_Core->run()
#8 {main}

#0 /home/leaderle/public_html/collections/application/libraries/Zend/Controller/Front.php(965): Zend_Controller_Plugin_Broker->postDispatch(Object(Zend_Controller_Request_Http))
#1 /home/leaderle/public_html/collections/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(97): Zend_Controller_Front->dispatch()
#2 /home/leaderle/public_html/collections/application/libraries/Zend/Application.php(366): Zend_Application_Bootstrap_Bootstrap->run()
#3 /home/leaderle/public_html/collections/application/libraries/Omeka/Core.php(165): Zend_Application->run()
#4 /home/leaderle/public_html/collections/index.php(28): Omeka_Core->run()
#5 {main}