Can prednisone or cellcept (mycophenolate mofetil) cause memory problems or cramping in the muscles?

Yes: Cellcept (mycophenolate mofetil) lists them as known side EFX. Prednisone notes muscle weakness and pain, confusion and trouble thinking clearly. But if required (discuss w/ physician) it's worth the risk for optimizing survival chances. So, do talk about it until you feel okay w/ it. Hopefully, it's short term and you'll return to being yourself.