X-Window DISPLAY variable
FYI, if you have the X-window DISPLAY variable set to a remote machine when you start OpManager, and that remote machine is/becomes unavailable, it throws an error in OpManager when attempting to login. The StartOpManagerServer.sh script only checks that the DISPLAY variable is set, not whether it's set to the local machine where OpManager is running. The default behavior should be to run headless if either the DISPLAY variable is not set, or is set to something other than the local machine.