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_attributes a,
(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_sortkey between 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