Deleting Problem

Here is my problem

I have a level structure which is 5 levels deep with 6 tables, for this
example i will call it table1,table2,table3,table4,table5,table6

(1)table1
(2)table2
(3)table3
(4)table4
(5)table5,table6
(6)table7,table8

table5 and table6 have fk keys pointing to table1,table2,table3,table4.
table7 and table 8 have fk keys pointing to table5.

Here is my problem i have delete triggers on table5 and table6 which
update summary information on table1,table2,table3,table4 if table5 or 6
gets delete, problem i am faced with is when eg table1 record gets
deleted i get the following error Error insert or update on table5
violates foreign key constraint "table4". They are all link with a
cascade delete.

Machine Windows 2003, Postgresql 8.1.4

Any help would be useful.

Thank you.