duplicate key

hi,

medias=> insert into medias (name, location) values ('BLABLA',
'Montreal');
ERROR:  Cannot insert a duplicate key into a unique index


Here's my database & tables :

Database    = medias
+------------------+----------------------------------+----------+
|  Owner           |             Relation             |   Type   |
+------------------+----------------------------------+----------+
| postgres         | medias                           | table    |
| postgres         | medias_media_id_key              | index    |
| postgres         | medias_media_id_seq              | sequence | 
+------------------+----------------------------------+----------+

Table    = medias
+----------------------------------+----------------------------------+-------+
|              Field               |      Type                    | Length|
+----------------------------------+----------------------------------+-------+
| media_id                         | int4 not null default nextval('"
|     4 |
| name                             | text not null                   
|   var |
| location                         | text                            
|   var |
+----------------------------------+----------------------------------+-------+


I don't specify a value to media_id, so why i got this error? It's
supposed to increment by itself (media_id serial). But, i have to say
that i import the data in medias with the function copy from... i import
also media_id information. Maybe now, i cannot add because my
medias_media_id_seq do not correspond to my new "importation". How can I
fix that?

Thank you very very much and once again sorry for my english.
Patrick