Oracle Forms

I am using Oracle Forms 6i, and am having problems with a form that doesn't allow a user to make an operation on the system. When this user, user1, tried to save a form after filling the info. and tries to save the changes it presents to them an error: frm - 40506 oracle error : unable to check for record uniqueness, I've searched this problem and it indicates that you have to GRANT permissions for the tables that it is trying to update or manage, I've already done this and still it presents me this same problem, it works fine with other users.