Had this message on a test box when I logged in as admin. I havent tried logging into it this week, and noticed that when I tried to the first time the Plesk panel was not responding because the psa service was also not running, although it was running the last time I had used it (last week).
# cat /var/log/sw-cp-server/error_log
2012-10-29 04:04:44: (server.c.1543) server stopped by UID = 0 PID = 1012020
Failed to update Panel. You can send the update log to Parallels support to try fixing the issue.
Error
Internal error: File specified by 13b36eb4-27fa-0c0f-e51b-891efaeaea46 was not found
Message File specified by 13b36eb4-27fa-0c0f-e51b-891efaeaea46 was not found
File /usr/local/psa/admin/plib/CommonPanel/Update/LogFile.php
Line 36
Type Smb_Exception_NotFound
Stack trace #0 /usr/local/psa/admin/panel/application/controllers/UpdateController.php(122): CommonPanel_Update_LogFile->__construct('13b36eb4-27fa-0...')
#1 /usr/local/psa/admin/plib/Zend/Controller/Action.php(513): UpdateController->logAction()
#2 /usr/local/psa/admin/plib/Zend/Controller/Dispatcher/Standard.php(295): Zend_Controller_Action->dispatch('logAction')
#3 /usr/local/psa/admin/plib/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#4 /usr/local/psa/admin/panel/application/library/AdminPanel/Application/Web.php(20): Zend_Controller_Front->dispatch()
#5 /usr/local/psa/admin/panel/application/public/index.php(15): AdminPanel_Application_Web->run()
#6 {main}
# ls -la /usr/local/psa/admin/plib/CommonPanel/Update/LogFile.php
-rw-r--r-- 1 root root 1.8K Jun 8 02:34 /usr/local/psa/admin/plib/CommonPanel/Update/LogFile.php