These are the results I got with my demo app:

// For application logfile:
--
RecordNumber: 26135
DateTime: 31.08.2013 21:32:15
EventType: Information
ID: 4120
Category: 1
MessageText: 
UserName: // Issue?!
ComputerName: // Issue?!
--

// For security logfile (UAC!!!):
--
RecordNumber: 97703
DateTime: 31.08.2013 21:44:16
EventType: Success Audit
ID: 5061
Category: 12290
MessageText: 
UserName: User SID not found // Issue?!
ComputerName: Lukas-PC // Works only here!
--

// For system logfile:
--
RecordNumber: 70504
DateTime: 31.08.2013 22:09:31
EventType: Information
ID: 7036
Category: 0
MessageText: 
UserName: User SID not found // Issue?!
ComputerName: // Issue?!
--