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(at)tissat(dot)es
TISSAT mailto (home): echiner(at)abonados(dot)cplus(dot)es
Av. Aragon, 30, 5ª planta Phone: 96 393 9950
Valencia (SPAIN)