error on start

Our Linux admin just upgraded our server to fedora Core 2 which apparently upgraded postgres to version 7.4.2-1

Now on trying to start the postgres server we get the following error:

An old version of the database format was found.\nYou need to upgrade the
data format before using PostgreSQL.\nSee (Your System's documentation
directory)/postgresql-7.4/README.rpm-dist for more information.

Can someone give me some insight into this please? The database was not touched. Should it have been dumped and restored in upgrading from 7.3.4?

thanks
Jodi