JDBC : CallableStatement returns always same Exception

Hi, I'am using a PGSQL DB on Linux, and I'm writing a Connection Servlet
to that DB.
Everything is fine when using simple statements, but I can't use any
CallableStatement to execute stored procedures.
It returns an exception , whatever I put in the prepareCall (even if
nothing) :

Error : Callable Statements are not supported at this time.
State : null
Code : 0

My code :
CallableStatement instruction ;
instruction = con.prepareCall("call ps_ins_user{?,?}"); --> raises
the Exception
...
or instruction = con.prepareCall(""); --> raises the Exception as well

Does that mean that stored procedure are not supported on pgSQL :-(?

I feel that this is a postgreSQL problem, because I've checked on the
JDBC forum, and others are using the same code on other database without
any probem.

Thanks for your help.

Bruno Faure