MATLAB added a new built-in function called ishermitian in 2014a. Apparently you have one of your own on the path. Type "which -all ishermitian". Locate any that do not belong to MATLAB's official toolboxes. Rename those to something else. If they do exactly the same thing as the built-in ishermitian, you're done. If they do something else, then you will need to find all uses of ishermitian in your code and change these to call whatever you named your ishermitian function to.