we have same problem too, firstly i've used open manager with firmware 3.41, it work. for last 3 weeks i've try multimanager ver.2.06. and rogero manager ver 8.02, upgrade my firmware to 3.55 cfw kmeaw waninkoko, guest??, my COD Black Ops doesn't work.
sure, it doesn't work coz i've change my firmware to 3.55. so far i tried to fix permission before launch the game, and make change eboot fix and param. iso to original, which get me back to XMB when launching from mounting disc. i don't have any idea now.