workbench can't create a table

[Thijs Hakkenberg]

  Dear list,

I have a workbench file which forward engineers OK. However, one table 
can't be created:
Executing SQL script in server

ERROR: Error 1005: Can't create table './mydb/UserCriterion.frm' (errno: 
121)
CREATE  TABLE IF NOT EXISTS `mydb`.`UserCriterion` (
   `idUserCriterion` INT NOT NULL AUTO_INCREMENT ,
   `idUser` INT NULL ,
   `idEvaluationCriterion` INT NULL ,
   `UserCriterion` INT NULL ,
   PRIMARY KEY (`idUserCriterion`) ,
   INDEX `idUser` (`idUser` ASC) ,
   INDEX `idEvaluationCriterion` (`idEvaluationCriterion` ASC) ,
   CONSTRAINT `idUser`
     FOREIGN KEY (`idUser` )
     REFERENCES `mydb`.`User` (`idUser` )
     ON DELETE NO ACTION
     ON UPDATE NO ACTION,
   CONSTRAINT `idEvaluationCriterion`
     FOREIGN KEY (`idEvaluationCriterion` )
     REFERENCES `mydb`.`EvaluationCriterion` (`idEvaluationCriterion` )
     ON DELETE NO ACTION
     ON UPDATE NO ACTION)
ENGINE = InnoDB
SQL script execution finished: statements: 26 succeeded, 1 failed

all other tables are created without problem.
Anyone knows what's causing this?

Regards,

Thijs H