Connecting from Java to PostgreSQL

Having a strange problem with Sun studio 4 update 1 talking to postgreSQL
7.2. (Redhat version)

Using the latest Postgres JDBC driver (both latest stable and dev
releases)- in Sun studio I'm having problems mapping my container manager
persitence entity beans to postgres tables.

I make a database schema and entity bean from the postgres datasource
(everything's fine at this stage) but when I try to map
the ejb fields to tables in the postgres schema, for deployment, the
dialogue reports "Table 'x' has no primary keys defined"

I've checked my keys and indexes and I definitley have a primary key
defined. Is there something I'm missing?

I have the database in MySQL also and it works fine with Sun - but I'd much
rather have a postgres backend.

I've searched the web and newsgroups and can find hardly any information on
this topic, your help would be very much appreciated

regards
Nuno D. Leitao