Foriegn key constraint

Hi,

I have a question. I tried adding a Foreign Key constraint to a table via the ALTER TABLE command. But the records in the table did not match with those in the Parent table. Now my Alter table command, instead of giving me an error of kind - 'records do not match', has gone into a kind of Deadlock between the 2 tables. I am not able to select from the tables, nor delete them, nor drop them. If I try to do any of these, I get the error saying -
" Error : RelationBuildTriggers: 2 record(s) not found for rel invoice"

How do I overcome this error. Any ideas will be greatly appreciated.
Thanks a lot in advance.

Shiva.