It's most likely your computer. Try verifying the game cache. I doubt this has to do with the MW2 Liberation mod.
I similar issues when I used my old laptop. I had this 24-inches monitor connected as mainscreen. It messed up everything for the game, so I was unable to launch. I disconnected the monitor and tried again. It worked fine.
And on another note. This sure has nothing to do with GSC modding.