How can I define circular referential integrity constraints?

I have two tables mutually referencing each other, and I get this error when trying to insert into one of them: "Foreign key constraint is incorrectly formed".

I have been stuck for three weeks this assignment and can't seem to get anywhere or find someone with database experience to help.

I have attached all three queries but only receive an error on the last query where I create the table "DEPARTMENTS"

CREATE DATABASE k0310855_AMAZON;USE k0310855_AMAZON;

my tables:

CREATE TABLE EMPLOYEE (EMP_ID int PRIMARY KEY,EMP_SALARY int,EMP_PHONE varchar(255),EMP_DEPARTMENT varchar(255));

and:

CREATE TABLE CHILDREN (    CHI_NAME int,    CHI_AGE int,    EMP_ID int,    CONSTRAINT CHILDREN PRIMARY KEY (EMP_ID, CHI_NAME));

and:

CREATE TABLE DEPARTMENTS (  EMP_DEPARTMENT int PRIMARY KEY,  DEP_NAME varchar(255),  DEP_BUDGET int,  DEP_MANAGER varchar(255),  CONSTRAINT FOREIGN KEY (DEP_MANAGER) REFERENCES EMPLOYEE (EMP_DEPARTMENT) );**

I am receiving the following error:

ERROR 1005 (HY000): Can't create table `k0310855_AMAZON`.`DEPARTMENTS` (errno: 150 "Foreign key constraint is incorrectly formed")