Postgres

Hi to list,

I had my database installed in my Slackware 7.0 (kernel 2.2.6). I was
using postgres 7.1 version. Now the database got corrupted. I had no clue
how it got corrupted. Basically, i did found that the data of various
users existing (in /usr/local/pgsql/data directory). But there were no
data existing in the following system catalogs.

pg_database. (except template0 & template1)
pg_shadow.   (except postgres user. Previously 15 users were there.)
pg_tables.   (Not showing any user created tables. Only system tables
get displayed).

But the data structure of individual tables exist somewhere. Suppose if i
do 'select * from tablename' then field names gets displayed but says 'no
rows'. At the same time, i am unable to get the structure through
\d tablename. 

Is it possible to recover the data in any way. I am having a old dump of
data which i can use to reinstall but i wanted to know how it happened in
the first place. Atleast, i can take some steps so that it doesn't happen
again.   

Could some one there help me out to recover the data.
Any help would be appreciated.

Regards,
Guru Prasad