problem in deleting contacts

Cannot delete contacts if i select the " all n records" radio, and then use. task action "delete contacts".

1. Basic search.
2. Narrow your search using A to Z pager. let's say "Z". (i got 9 records).
3. Then select radio "all 9 records".
4. Select Task action "Delete Contacts".
5. Then i get following message "Number of selected contacts: 134". (although selected records were 9). 134 is the total no of records in my db.
6. Then when i click on "delele contacts" page breaks down. i get following error:
user error: Cannot delete or update a parent row: a foreign key constraint fails