if its anything like the ps3 nothing about your online play is stored on your system. and if you have lost rankings its because gaming companys use servers to power up the online play. these probably have a format on them at some point. but its only what i am guessing. so please if i am wrong dont start with all the gaming geek stuff
Copy the whole profile folder and unistal and reinstal game and patches then drop the folder back in, cross fingers and hope for the best, if that doesnt work I may know a slightly quicker way of levelling to 65