Problem with timestamp and primary key.

When I try to execute this sentence:

CREATE TABLE ACCESO(
USR_CODIGO        VARCHAR(20) NOT NULL DEFAULT '0',             --Código
del usuario
SER_CODIGO        VARCHAR(10) NOT NULL DEFAULT '0',             --Código
del servicio
ACC_FECHAA        TIMESTAMP NOT NULL,
ACC_FECHAZ        TIMESTAMP,
CONSTRAINT C_ACC PRIMARY KEY (USR_CODIGO,SER_CODIGO,ACC_FECHAA));

I get this error message:

NOTICE:  CREATE TABLE/PRIMARY KEY will create implicit index c_acc for
table acceso
ERROR:  Can't find a default operator class for type 1296.
EOF

Does anybody know what could be the problem. What should I do?
The problem is that I could subtitute TIMESTAMP with DATE or DATETIME
but that's not compatible with Oracle's DATE and, when I try to access
the table with JDBC in Oracle works fine but in Postgres it needs to be
Timestamp.
Please help,
       Esteban

------------------------------------------------------------Esteban Chiner Sanz        mailto (work):
echiner@tissat.esTISSAT                    mailto (home): echiner@abonados.cplus.esAv. Aragon, 30, 5ª planta  Phone: 96
3939950Valencia (SPAIN)