Event Log not Logging ??

 Hi All,
 On my dev machine when I log errors to the event log all works great however when I move the web application to the test server the events are not being logged... I am hoping it is some configuration issue with IIS however I am totally lost.
The code writing the events: EventLog.WriteEntry("xxxxx", err, EventLogEntryType.Error);  
Any help will be appreciated.
 Thanks,
Neil 

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