Primary key violation

Sir,

We were using postgresql for our development for two years. The database which we are using is having no problem till last week.Now we are using version 7.2 of postgresql.

In this week, we got two major bugs in database. They are,
1 . Once we could see that a record is inserted into a table with violation of primary key. Primary key is numeric type. Then we checked the oid of these two records. The oids are also same! How this happens ?

2. When we give a query like "select token_no from member_master where token_no = 1290" gives an output "No record found". But when we give another query like "select * from member_master where token_no = 1290" gives one record showing the token_no as 1290.Token number is also numeric type.

Sir, does these happen due to our mistake or some database failure ?

Awaiting reply,
Baiju MP