The local computer may not have the necessary registry information or message DLL files to display messages from a remote computer

It clearly misidentified the file C:\WINDOWS\Media\SSRoam.wav as viral (or maybe not even). I would go into the exceptions list, and add that file as an exception, and replace it with a known-good version.

The windows event log really doesn't contain event descriptions. It only contains event numbers, and Windows tries to resolve those numbers to descriptions when you view the logs. An application that adds log entries should install a number-to-description translation table.

The error message "The description for Event ID ( 0 ) in Source ( Leaftrade Alerts ) cannot be found. " means that Windows either could not find a table for Leaftrade Alerts, or that the table missed entry 0. It's an error message from Windows itself, so you can get similar error messages for different Sources.

Note however that Windows did manage to catch one part of the event coming from Leaftrade Alerts. The "LeaftradeLauncher::Tem.InitClient sucessful. Initialized with server:servlet" part doesn't come from Windows, but directly from LeaftradeLauncher. So, it seems that LeaftradeLauncher itself thinks that it started succesfully.

Based on the version you list you have Symantec Endpoint Protection 11.0.6300 and not Norton. Is that correct? Is the system running a management server (SEPM) Do you use application and device control? If managed, are there event log entries on the SEPM that can shed more light on this? Or log entries in the Symantec Client itself?