ORA-00054 referring to the table you are trying to update it is already locked by another session that made a query for an update on the same table and not committed or rolled back yet. It could be a form or another session.

The action you could take to solve the problem is to commit or roll back the changes from the other session, causing the lock before performing the current action. There is a query also to help you identify which session that causing the lock on your table so that you can kill the session immediately.

SELECT S.USERNAME
,S.SID
,S.SERIAL#
,T.USED_UBLK
,T.USED_UREC
,RS.SEGMENT_NAME
,R.RSSIZE
,R.STATUS
FROM V$TRANSACTION T
,V$SESSION S
,V$ROLLSTAT R
,DBA_ROLLBACK_SEGS RS
WHERE S.SADDR = T.SES_ADDR
AND T.XIDUSN = R.USN
AND RS.SEGMENT_ID = T.XIDUSN
ORDER BY T.USED_UBLK DESC;

Above query has been taken from oracle-base then from the output of above query you can use SID and SERIAL# to kill the session by executing the following statement.

alter system kill session 'sid,serial#' IMMEDIATE;