MySQL ERROR 1016 (HY000): Can't open file

I just got this error message on one of my mysql databases. It sounds kind of bad, but to fix it I just ran the following SQL statement, and all was well:

REPAIR TABLE tablename

The error might look like on MyISAM tables:

ERROR 1016 (HY000): Can't open file: 'tablename.myi' (errno: 1)

Or like this on InnoDB tables:

ERROR 1016 (HY000): Can't open file: 'tablename.InnoDB' (errno: 1)