Modern Warfare 2 Problem/Question

Hello Members,
When I try to run Call of Duty: Modern Warfare 2 single play everything works fine as suspected.
As when I try to launch the multi-player version, this is the error I obtain.
“Fastfile for zone ‘localized_code_post_gfx_mp’ is newer than client executable (version 387, expectin 276)”
How would I go upon fixing this error, and I downloaded the copy from .
Answer #1
http://compuparadise.com/blog/featured/how_to_fix_call_of_duty_world_at_war_fasfile_for_zone_code_107_error/
only thing i could find
Answer #2
Yeah, I checked on that site, couldn’t find anything that could help.
Searched Google a few times, but couldn’t find anything that was for “downloaded copies”.
Answer #3
Maybe the problem is on the game version?
Answer #4
Well how would I ago upon, “downgrading my client” to the version I need?
Answer #5
you need to update your client version I assume….are you using alteriw by any chance? or legit?