This error means that the game was unable to patch properly. The downloaded data might be corrupted.
1. Reboot your computer and try again.
2. Your Temporary Internet files might need to be cleared.
-A. For Internet Explorer users: Click on Tools, select Internet Options and click on Temporary Internet files (or “Delete…”) from the General tab. Select “Delete Files”. This may take several minutes. Once it’s done, download Combat Arms again.
-B. For Firefox users: Click on Tools, select “Clear Private Data” and then click on “Clear Private Data Now”. Once it’s done, download Combat Arms again.
3. Your download manager could be corrupting the downloaded files. If you have a software that you use to manage or accelerate your downloads, turn it off and download Combat Arms without it.