sequenc_name.currval not defined

Hi,

I keep on getting the following error when I attempt to insert a new record:

SELECT * FROM table_name WHERE tableid = currval('tableid_seq');

PostgreSQL said: ERROR: tableid_seq.currval is not yet defined in this
session.

What's weird about this problem is that I have a script that
successfully performs this action.

Thanks for your help,

Mark