WinServer2008 R2 , .net service, local system account

Hi,
This is marginally on topic (I hope)
Wrote the simplest service as per the walkthrough, on my WinServer R2
based Development platform.

The service uses an event log to to record the fact that it has opened
and closed.

It installs OK but when I attempt to start it gives a security
exception which appears to be related with trying to instantiate the
log.

I went back to my old WinServer 2003 platform and did the same thing
and it starts / stops OK.

So I guess I am asking how do I get the Local System account to get
access to the event logs on WinServer 2008 R2.
thanks
Bob