That's weird.
I get the same error except it only happens sometimes when I try to Start the Game; but the game actually starts after I exit the error code.
If you're downloading the Combat Arms Downloader, try to download the setup another way.
There's something that says:
below the option to download the CA Downloader on their official website.If you have download problems with the Downloader, or would prefer to get the game client the old fashioned way, click here.