When checking my MySQL databases, most were OK but I saw a message
myisamchk: File '(built-in)' not found (Errcode: 2)
This looked wierd. But I eventually tracked this down to the fact that two tables has an Index field specified as FULLTEXT. Once this index was removed, everything wasw OK.
The really wierd aspect was that checking a single table, the error did not appear, but checking multiple tables the error showed up on the second table that had an index of FULLTEXT. The first table that had an index of FULLTEXT did not have a problem! Wierd!