Haar cascade - problem with xml file

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I used 188 positive images and 299 negative images to train my classifier. After 20 stages the process stack. I notices that in previous stage the FA was zero (0). I do not know why happen that so I take the 20 stages to create the xml file. When I use the xml file to my program can not detect any of my object.

Please, can anyone help? I create many xml files and I have the same problem