Post stopped due to error "Poster: Unexpected Oracle error: ORA-30554: function-based index <i (4265250)

Post is stopped due to error and the following entry appearing in the event log points to the error:

Notice 2009-09-22 23:54:02.810183 876998 772 Poster: ORA-30554: function-based index OWNER.INDEX_NAME is disabled. (posting from SID, queue Queue_name, to SID) [module osp]
Error 2009-09-22 23:54:02.810506 876998 772 Poster: Unexpected Oracle error: ORA-30554: function-based index OWNER.INDEX_NAME is disabled. (object name: OWNER.TABLE_NAME) (posting from SID, queue Queue_name, to SID) [module opo]
Info 2009-09-22 23:54:02.856590 729584 1 Poster exited with code=1, pid = 876998 (posting from SID, queue Queue_name, to SID)

Issues with function based index is causing the Post error.

Carry out the following steps to correct the problems with index and restart Post:

1.SQL>alter index OWNER.INDEX_NAME enable;
2.sp_ctrl>start post

If the above does not help, then carry out the actions of dropping the index, rebuilding it and enabling it before starting Post. See Additional Information section for details.

The following are the details on the ORA-30554:

ORA-30554:function-based index string.string is disabled

Cause:An attempt was made to access a function-based index that has been marked disabled because the function on which the index depends has been changed.

Action:Perform one of the following actions: -- drop the specified index using the DROP INDEX command -- rebuild the specified index using the ALTER INDEX REBUILD command -- enable the specified index using the ALTER INDEX ENABLE command -- make the specified index usable using the ALTER INDEX UNUSABLE command