[JohnWoo]

then what error message you have when you "can't post or delete threads"?
and i still think that 9 hours is not normal...
and still recommend to try again

ALTER TABLE post DROP INDEX pagetext
after it
ALTER TABLE post DROP INDEX title
after it
FLUSH TABLE post
after it
REPAIR TABLE post
after it
ALTER TABLE post ADD FULLTEXT (title)
after it
ALTER TABLE post ADD FULLTEXT (pagetext)
and after it
OPTIMIZE TABLE post

Nearly sure that it must take less then hour summary