This is a small SBS 2008 network which has been experiencing intermittent problems accessing the server. When the problem is occurring the server can be "pinged" from other computers but Outlook will not connect to the Exchange Server (which is running on the server) and files cannot be accessed. I can connect remotely using RDP. After a period of time the problem resolves itself but will recur several days or weeks later. When the problem is occurring the system logs show a problem with what I think is the USB drive used for the backup (using native Windows backup) e.g. it reports an error on Drive \device\harddisk\DR7 and "System failed to flush data to the transaction log. These errors seem to occur at about midnight and repeat over several hours. I would like to find out if others have experienced this sort of problem and if it is possible that a faulty USB External drive could cause this sort of problem with the server.