Andy,
Did you ever get an answer to your question? I am currently running SCCCM 2007 R3 with SQL 2005 SP2 and SRS 2008. Everything is working from both the ConfigMgr Admin Console and by accessing reports directly from the SRS website except that I am receiving the "SMS SRS web service is not running on SRS Reporting point server "XXXXX" 7403 error every hour.