No suitable driver error trying to connect to postgresql from jdeveloper

Anyone have this problem? Usually it is because of a classpath error
but I have copied my jar file(s) into the jdeveloper/jdbc/lib
directory (where the oracle jdbc drivers are ...) and tried the
following:

Connection Type : 3rd Party JDBC Driver


Username and password correct (verified using pgAdmin)

Driver class : org.postgresql.Driver

Classpath : I have tried all 4 drivers that come with postgresql 7.5
-- pg74.214.jdbc1.jar, jdbc2.jar, jdbc2ee.jar and jdbc3.jar.

url : localhost:5432 (this works in pgAdmin)

... no dice. Any clues? My connection to Oracle 9i from jdeveloper
works fine ... As does my pgAdmin connection to postgresql ...

Many thanks!
syg