BizTalk Database CPU utilization

 I am having issues with a SQL 2005 sp2 database that hosts all the biztalk databases.  The server slowly consumes more and more CPU throughout the day until eventually the biztalk database jobs begin talking an extended time to complete and perfmonance is adversely affected.  I have found, by restarting the SQL Agent, CPU utilization returns to normal until the next day.  I am running BizTalk 2006 R2 and the database is on a Windows 2003 cluster.  Has anyone one else had simliar issues?