SQL Server 2005 error log, could not read information for this log entry

Hi,

There is a SQL Server error log entry in the SQL Server 2005 production box with the following.
 

“Log Viewer could not read information for this log entry. Cause: Data is Null. This method or property cannot be called on Null values.. Content:”
 
Has anyone seen anything similar? Does anyone know what this mean and how I can debug this and get the process that is logging this to the SQL Server error log?

Thanks