Failed to create temporary file

Hi!

I'm doing a select (from an OACS page or from psql) and I get:
ERROR:  Failed to create temporary file pgsql_tmp/pgsql_tmp27212.775

The same select work ok a different database (which is on a different
machine)

the select is :
select a.attribute_id, a.pretty_name,          a.ancestor_type, t.pretty_name as ancestor_pretty_name     from
acs_object_type_attributesa,          (select t2.object_type, t2.pretty_name,    tree_level(t2.tree_sortkey) -
tree_level(t1.tree_sortkey)+ 1 as
 
type_level             from acs_object_types t1, acs_object_types t2     where t1.object_type = 'group'       and
t2.tree_sortkeybetween t1.tree_sortkey and
 
tree_right(t1.tree_sortkey)) t    where a.object_type = 'group'      and t.object_type = a.ancestor_type   order by
type_level