BO4 - errors in event log to do with session management + ora-07445

Hi,

Our dba team is reporting ora-07445 error messages on the reporting database at about the same time as errors in event log

Failed to determine status information of file/directory C:\bo4\SAP BusinessObjects Enterprise XI 4.0\Data\<server_name>_6400\BIPROD01.WebIntelligenceProcessingServer1\sessions\_ARbMBLFfaYlOkIk8.mI4xzA\P0pi7164KT392{<server_name>}{<server_name>.WebIntelligenceProcessingServer1}{ARbMBLFfaYlOkIk8.mI4xzA}.tmp from the file system. Please check for file system corruption, permissions and sharing violation

We are using bo4 sp6.

These errors are intermittent.

Running 2 node windows 2008 cluster with bundled tomcat + cms + repoprting database oracle 11.2. 03.

Ant thoughts/advice?

Thanks

Philip