Error on Programming Assignment

That error message is very specific. Are you sure no syntax errors occur if you do “Cell → Run All”? Have you tried searching the notebook for the string “dj_dw_ij =” to see if there is anything funny there?

It is a legitimate theory that something is damaged about your notebook. If you want to try with a clean copy, there is a topic about that on the MLS FAQ Thread (see topic B.5).