timestamp error cant find class for type 1296

When attempting to create the following table:

CREATE TABLE test (
id timestamp primary key,
fodder varchar(64)
);

I get the following error:
ERROR: Can't fine a default operator CLASS for type 1296

Whats that all about? ;)

If I create the table as follows (which AFAIK is equivilant):
CREATE TABLE test2 (
id datetime primary key,
fodder varchar(64)
);

It creates fine but when I try to insert something like:

INSERT INTO test2 (fodder) VALUES ('arfarf');

I get:
ERROR: ExecAppend: Fail to add null value in not null value attribute id

I thought that the datetime field would be filled automatically on a insert with a current timestamp. can someone point out what Im doin wrong.

Thnx all,
-crypt0genic

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