After closing the browser (new session) I can manually delete the contacts.
However I choose to access the database directly and deleted the contacts from there. You will have to delete the referenced table entries first before you can delete the contacts themselves. For later reference, here is what I did:
connect to postgresql, login etc... then execute the following commands (replace the query criteria by the criteria of your choice):
delete from contact_address where contact_address.contact_id in
(
select contact_address.contact_id from contact_address, contact
where contact_address.contact_id = contact.contact_id
and contact.notes like '%bubu%'
)
;
delete from contact_emailaddress where contact_emailaddress.contact_id in
(
select contact_emailaddress.contact_id from contact_emailaddress, contact
where contact_emailaddress.contact_id = contact.contact_id
and contact.notes like '%bubu%'
)
;
delete from contact_phone where contact_phone.contact_id in
(
select contact_phone.contact_id from contact_phone, contact
where contact_phone.contact_id = contact.contact_id
and contact.notes like '%bubu%'
)
;
-- finally delete the contacts after we have deleted all references entries
delete from contact where contact.notes like '%bubu%';
Cheers
Boris