Upgraded to Red Hat 7.1, now my DB is toast?

I had PGSQL up and running fine on RH6.2 (whatever version comes with
RH6.2).  For some fool reason, I thought I'd upgrade to 7.1.  While
reconfiguring my system after having almost all of my settings
mysteriously vanish, I finally get to starting up postmaster and get
this error:

/usr/bin/postmaster does not find the database system.  Expected to find
it in the PGDATA directory "/var/lib/pgsql/data", but unable to open
file with pathname "/var/lib/pgsql/data/base/template1/pg_class".

No data directory -- can't proceed.

Ack.  The /var/lib/pgsql/data/base does exist but there is no template1
dir...  Does this mean that DBs made with 6.whatever are incompatible
with 7.whatever?  And if so, is there a way to recover/upgrade/save the
db I already have?  Thanks in advance for any advice.  Later,

J. J. Franzen