I just tried to play online and when I click on the matches it says serial code is in use. I preorded Crysis 2 from the EA website as a download and after that and moved the location of the files to my other hard drive and now I try to play online and it says that.

Miine said that to. I think you have to include the dashes every 4 digits

At the log in window at the bottom of the window that's where you have to re-enter your code to play on-line