Can't create foreign key

[jc]

I'm trying to create a foreign key by executing the following statement:

ALTER TABLE `cc`.`takenlessons` 

  ADD CONSTRAINT `fk_lessons`

  FOREIGN KEY (`LessonID` )

  REFERENCES `cc`.`lessons` (`id` )

  ON DELETE CASCADE

  ON UPDATE NO ACTION

, ADD INDEX `fk_lessons` (`LessonID` ASC) ;

 

I'm using the RC of MySQL workbench to do this. When I execute this
statement, I get the following error:

Error Code: 1005

Can't create table 'cc.#sql-115c_61' (errno: 121))

 

In the past when I got a similar error, it was because the fields didn't
match exactly. For instance, one may be Int(10) and one Int(11), or one may
be Unsigned, and the other not.  But, in this case, both match exactly.
What other reasons are there for a foreign key creation to fail like that?

 

Thanks,

Jesse