It seems actually not my case because I have primary key and my unique key is not single (composite).
I had this error only one time and can't reproduce it anymore after many attempts.
121128 15:58:36 [ERROR] Slave SQL: Could not execute Update_rows event on table db.g_character;
Can't find record in 'g_character', Error_code: 1032; handler error HA_ERR_KEY_NOT_FOUND;
the event's master log FIRST, end_log_pos 138, Error_code: 1032
121128 15:58:36 [Warning] WSREP: RBR event 2 Update_rows apply warning: 120, 2846616
121128 15:58:36 [ERROR] WSREP: Failed to apply trx:
source: 7750bfd2-3951-11e2-0800-6ac93456152e version: 2 local: 0
state: APPLYING flags: 1 conn_id: 219 trx_id: 49650137
seqnos (l: 2871111, g: 2846616, s: 2846615, d: 2846564, ts: 1354103916789135518)
121128 15:58:36 [ERROR] WSREP: Failed to apply app buffer: l..P^S, seqno: 2846616, status: WSREP_FATAL
at galera/src/replicator_smm.cpp:apply_wscoll():49
at galera/src/replicator_smm.cpp:apply_trx_ws():120
121128 15:58:36 [ERROR] WSREP: Node consistency compromized, aborting...
Create Table: CREATE TABLE `g_character` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`guid` int(10) unsigned NOT NULL,
`gid` smallint(5) unsigned NOT NULL,
`wid` int(10) unsigned NOT NULL,
`fid` smallint(5) unsigned NOT NULL,
`val` int(10) unsigned NOT NULL,
`updated` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
UNIQUE KEY `atom` (`guid`,`fid`,`gid`,`wid`),
KEY `updated` (`updated`),
KEY `fid` (`fid`),
KEY `gid` (`gid`),
KEY `wid` (`wid`),
) ENGINE=InnoDB