Postgres mystery

Can anyone tell me what the problem is here:
I am inserting into a table via a stored procedure, to a few columns within the table and postgres is throwing a
CANNOT EXECUTE NULL QUERY.

<code snip>
EXECUTE ''INSERT INTO table (column1, column2, column3, ''||quote_ident(column4)||'') values (''||quote_literal(RECORDNAME.column1)||'',''||quote_literal(RECORDNAME.column2)||'',''''stringvalue'''',''||quote_literal(RECORDNAME.column2)||'')'';

</code snip>

Is this a bug, as I am ensuring that the NOT NULL columns are supplied, as well as one other.

Kind Regards,
Shaun Clements