Copy error?

Hi all,

Database: 7.1.3 (RPM)

OS: Redhat 7.1

Table: Create table jquserdata (

Username varchar(20) not null, primary
key,

)

Copy some corrupted data from a 7.1.3 (Encoding ASCII) with pg_dump, then
copy them (psql Ce gamedb <data) to a new database(Encoding EUC_CN), some
error reported (duplicate primary key), I erased these rows and re-execute,
finally all data copied, next ,vaccum Cz gamedb, this error still reported:

Cannot insert a duplicate key into unique index jquserdata_pkey !

Why? Everything is Ok when I use 7.0.2, but after I upgraded my database to
7.1.2 (next 7.1.3), things goes wrong. If no one can answer this question,
the only thing I can do is go back to 7.0.2. But how to downgrade a database