Using MW2 Liberation on one account will get the second account banned if you do not terminate the .temp files that are active after using Liberation, even after you close it, they are running in the background for a faster start up later on, terminate these programs before proceeding onto the account you do not want to get banned.
After some research I found out that was why I got banned on my second account wich I never used a console unlocker or any hack at all on.
Hope you did not start any mods on the ban-want account and then logged onto the ban-unwanted account.
Hope I helped.