duplicate key violates unique constraint

Hello all,

I have a table named "t_i_shift_shadow" with following spec

Column | Type |
Modifiers
-----------------+-----------------------+-------------------------------------------------------------------
cid | character varying(20) | not null
shift_rev_id | character varying(20) | not null
start_time | bigint | not null
end_time | bigint | not null
lunch_from_time | bigint | default -1
lunch_to_time | bigint | default -1
shift_date | date | not null
is_cyclic | integer | not null
serial | integer | not null default
nextval('t_i_shift_shadow_serial_seq'::regclass)
Indexes:
"t_i_shift_shadow_pkey" PRIMARY KEY, btree (serial)
Triggers:
_replcluster_logtrigger_4 AFTER INSERT OR DELETE OR UPDATE ON
t_i_shift_shadow FOR EACH ROW EXECUTE PROCEDURE
_replcluster.logtrigger('_replcluster', '4', 'vvvvvvvvk')

I am trying to replicate this table using slony.

But I get the following error... I wanted to know if this is a postgres
error ??? If it is what is causing it??

ERROR -->

PGRES_FATAL_ERROR select "_replcluster".setAddTable(8, 36,
'public.t_i_shift_shadow', 't_i_shift_shadow_pkey', 'shift shadow
table'); - ERROR: duplicate key violates unique constraint
"sl_table_tab_reloid_key"

I am a bit confused about where to post it.. So I am posting it here first...

Thanks and Regards,
Sweta.