PG crash on simple query

Hi,
I have consistent PG crash on some query,
so I was able to isolate a simple query that crash postgres...

SELECT p.docid FROM prod.t_documents AS p
INNER JOIN t_tempdocs AS t
ON p.docid = t.docid
LEFT OUTER JOIN prod.t_refs AS ct
ON ct.docid = p.docid;

It seems like any reference to prod.t_refs lead to that.

We run PG 7.3 on SunOS

Is there any particular steps to follow in order to resolve this.
Thank you.