ORACLE8I: Selective UPDATE doesn't work

[JA1]

I'm having a real problem with a selective update. It used to work (I'm sure?) and now doesn't.

The database is Oracle8i, bog-standard SQL no Plus or otherwise.
Sorry it is long, but the original SELECT was long and the update has to be specific...

UPDATE
PROC_MN,
PROC_OVERVIEW,
PROC_MAJOR,
PROC_MN_CON_ACT,
PROC_MN_CON_ACT_UPD
SET
PROC_MN.LAST_REPORTED_DT=TO_DATE('28-06-2005','dd-mm-yyyy')
WHERE
PROC_MN.PROC_MN_SEQ IN (SELECT DISTINCT PROC_MN_SEQ FROM PROC_MN WHERE PROC_MN.PROC_MN_SEQ >= 1 ) and
PROC_OVERVIEW.PROC_OVERVIEW_SEQ IN (SELECT PROC_OVERVIEW_SEQ FROM PROC_OVERVIEW WHERE PROC_OVERVIEW.PROC_OVERVIEW_SEQ=PROC_MN.PROC_OVERV IEW_SEQ) and
PROC_MN.PROC_MN_SEQ IN (SELECT PROC_MN_SEQ FROM PROC_MN_CON WHERE PROC_MN.PROC_MN_SEQ=PROC_MN_CON.PROC_MN_SEQ) and
PROC_MN_CON.PROC_MN_CON_SEQ IN (SELECT PROC_MN_CON_SEQ FROM PROC_MN_CON WHERE PROC_MN_CON.PROC_MN_CON_SEQ=PROC_MN_CON_ACT.PROC_M N_CON_SEQ) and
PROC_MN_CON_ACT.PROC_MN_CON_ACT_SEQ IN (SELECT PROC_MN_CON_ACT_SEQ FROM PROC_MN_CON_ACT WHERE PROC_MN_CON_ACT.PROC_MN_CON_ACT_SEQ=PROC_MN_CON_AC T_UPD.PROC_MN_CON_ACT_SEQ);


ORA-00971: missing SET keyword

I've tried stipping out the tables other than PROC_MN but then the other fields in the WHERE segment become invalid...

Can anyone out there help with my syntax?

Regards,

Jane.