mmorse please comment on this for accuracy.
- I completely uninstalled 5.0 as well as removing various locations on server such as in /etc. *Don't delete where ever your backup is*
- I then reinstalled the older version I was running. In my case the last version was 4.5.10.
- Then I rsynced over from my last backup which restored my last backup.
That "should" fix you right up and is what's suggested to restore in issues such as this.
PLEASE CONFIRM WITH A ZIMBRA PERSON!