BAR shuts down

NBU 7.5.0.6

master/media win 2008 r2

client win2003

backup of microsoft exchange information store started failing with error 13 'an exixting connection was forcibly closed by the remote host'. If I go to the client and start BAR. It comes up fine and shows the last backup of a couple of days ago. If I try and do a manual backup the BAR shuts down. Any clues what is happenening?