I am not able to reproduce the error. I took a sample data of same size as you mentioned and I am able to train the model for more than 100 epoch. You may want to share your data with me so I can investigate it. Although looking at the error I can guess this has to do with some row or column vector confusion. May be you are trying to access a row vector but which was actually defined as column vector. In short this kind of errors just mean you are trying to access an element which does not exist.