Sorry I should have updated the thread yesterday when I found the cause:This is a known bug - CSCtg47738Workaround is Reload - Fix is IOS upgrade to > 12.2.55SE----------------------------------------- CSCtg47738            Bug Details 3750,2960 - u...

Hi,I am experiencing the exact same problem on 2 of our devices (3750G stacks) running 12.2(50)SE4switch#copy running-config null:%Error opening system:/running-config (No such file or directory)switch#copy running-config runningbackup.txtDestination...