I was having the same problem, though my situation may be different because of my setup. I am running the xbox without an hdd, so I am using the onboardmu. When I go into the title update section to download a tu I choose the onboardmu device. It then downloads and I have the option to active the title update. I run the game and the bottom right corner with display TU0. I then noticed while in ftp or file manager that I have dir called /USBMUCache0/Cache/ so I copy the tu into this dir and run the game and it works. You can then go back into the active tu and I then delete the one for onboardmu and leave the usbmu0 active. Why this works idk, I have tried using memory cards with no luck as well. GL
