When I install rabbitmq-server package on Lucid, I always get a warning about upgrading from a previous version (even though no previous version is installed), and then I have to hit enter to dismiss the dialog. Is there any way to disable this prompt so I can do the install unattended?
Try adding to your preseed config (assuming you are preseeding, as "install unattended"):
rabbitmq-server rabbitmq-server/upgrade_previous note
If not doing unattended install, can pass these options to debconf-set-selections (as root):