Audit Failure Event ID 4674

I'm looking for the cause of this error in my Security Event Log. The server is Windows 2008 R2 Standard running Microsoft Lync 2010 with the integrated SQL (formally known as MSDE, I don't recall what they call it today). This error seems to occur about every 20 minutes or when manually running GPUPDATE. When it occurs I always get 3 in a row (never any more or less).

Log: Security
Task Category: Sensitive Privilege Use
Keywords: Audit Failure
Event ID: 4674

An operation was attempted on a privileged object.

Subject:
	Security ID:		LOCAL SERVICE
	Account Name:		LOCAL SERVICE
	Account Domain:		NT AUTHORITY
	Logon ID:		0x3e5

Object:
	Object Server:	LSA
	Object Type:	-
	Object Name:	-
	Object Handle:	0x0

Process Information:
	Process ID:	0x1e8
	Process Name:	C:\Windows\System32\lsass.exe

Requested Operation:
	Desired Access:	16777216
	Privileges:		SeSecurityPrivilege