Vista - Server 2008 App not logging to event viewer

I cannot get my application to log to the application event viewer in
server '08. it's strange as it works fine on one of my machines, but
not on two others (and all similarly configured, i'm running with
default security enabled on all 3 boxes, ...).

has anyone seen this before?

here's a sample except:

class Program
{
static string _eventSource = "evntSrc1";
static string _logAppName = "ServiceApplication1";
static int eventId = 33;

static void Main(string[] args)
{
if (!EventLog.SourceExists(_eventSource))
{
EventLog.CreateEventSource(_eventSource, _logAppName);
}

EventLog myLog = new EventLog();
myLog.Source = _eventSource;
myLog.WriteEntry("test msg1", EventLogEntryType.Error,
eventId);
}
}

thanks, dave