Have gone through several weeks of Outlook 2007 reporting that the PST file is damaged, for no apparent reason. Have tried letting Outlook PST Repair itself with no success and also leaving Outlook open so that the program shuts down in a more controlled manner with Vista SP1 on closing down the PC for that session, again with no success. Running SCANPST has provided patchy success (50/50) and slows things down whilst running. What seems to have worked is setting Outlook to Send/Recieve on Exit (via 'Tools', 'Options', 'Mail Setup', 'Send/Receive', tick 'Perform an automatic send/receive when exiting').