Dear Rob
may be check e.g.
http://scn.sap.com/message/8746770
http://scn.sap.com/thread/1464920
http://scn.sap.com/message/13933452
http://scn.sap.com/thread/1743361
http://scn.sap.com/thread/1800268
Most important. SAP note 1096697
or check e.g.
http://help.sap.com/saphelp_erp60_sp/helpdata/en/a7/28786d0a6c11d28a220000e829fbbd/content.htm
C.B.