There is a process documented at the back of the Zenoss Admin guide that says if you change the IP address or hostname then you effectively have to recreate your rabbit stuff. It is under section 14.8 - "Host Name Changes" and gives you the process to follow.
If you have a new install Zenoss 4.2.3, then you will also need to modify the documented instructions slightly because your AMQP password won't be zenoss - see this append http://community.zenoss.org/message/71139#71139 . If you upgraded from 4. to 4.2.3 then your password is probably still zenoss. Either way, check with $ZENHOME/etc/global.conf.
Other than that, the process should be quick, straightforward - and fix your problem!
Cheers,
Jane