If you are using SQL 2008 R2 for OpsMgr DB’s, you need SQL 2008R2 CU5

There is an issue where your SQL server hosting the OperationsManager database might consume large amounts of CPU for extended periods. 

This is due to a security cache issue when a non-sysadmin creates a heavy workload on a TempDB database.  Read more about this on the support team blog:

http://blogs.technet.com/b/operationsmgr/archive/2011/02/03/fix-sql-server-hits-100-cpu-utilization-when-there-are-configuration-update-requests-in-scom-2007.aspx

This SQL issue was first fixed in SQL Server 2008 R2 Cumulative Update 5 (CU5):

http://support.microsoft.com/default.aspx?scid=kb;en-US;2438347