PostgreSQL Duplicate key violates unique constraint error

[c.efrein]

CentOS 6.2 64bit Server
PostgreSQL 8.4.9 installed via yum

I am seeing errors from time to time in PostgreSQL's logs about the table called Events.

Zabbix is the only application using PostgreSQL.

Here is the error:

INSTRUCTION :  insert into events (eventid,source,object,objectid,clock,ns,value,value_changed) values (6393428,2,3,38,1353354000,0,1,0)
ERROR:  duplicate key violates unique constraint « events_pkey »

There is no sequence associated with the table events

Here is the table structure for events

			   Table « public.events »
Colonne    |  Type   |          Modificateurs           | Stockage | Description 
---------------+---------+----------------------------------+----------+-------------
eventid       | bigint  | non NULL                         | plain    | 
source        | integer | non NULL Par défaut, 0           | plain    | 
object        | integer | non NULL Par défaut, 0           | plain    | 
objectid      | bigint  | non NULL Par défaut, (0)::bigint | plain    | 
clock         | integer | non NULL Par défaut, 0           | plain    | 
value         | integer | non NULL Par défaut, 0           | plain    | 
acknowledged  | integer | non NULL Par défaut, 0           | plain    | 
ns            | integer | non NULL Par défaut, 0           | plain    | 
value_changed | integer | non NULL Par défaut, 0           | plain    | 
Index :
"events_pkey" PRIMARY KEY, btree (eventid)
"events_1" btree (object, objectid, eventid)
"events_2" btree (clock)
Référencé par :
TABLE "acknowledges" CONSTRAINT "c_acknowledges_2" FOREIGN KEY (eventid) REFERENCES events(eventid) ON DELETE CASCADE
TABLE "alerts" CONSTRAINT "c_alerts_2" FOREIGN KEY (eventid) REFERENCES events(eventid) ON DELETE CASCADE

Question

What steps can I take to resolve this error?

On Stackexchange, I have been told to add a sequence to Events, what effect would that have?

ALTER TABLE events ALTER COLUMN eventid TYPE bigserial;

[Colttt]

dou you create a Bugreport?!

i think this is abug