Bad file length means there's something going on with the game as it tries to download to your browser. What seems to happen sometimes is ISPs cache a version of the file that's not fully downloaded, which they then keep serving to you in order to save on their bandwidth instead of getting the file a second/third/fourth time.
This kind of error usually clears itself up once the bad cached version expires (or is cleared). Also our regular friday updates help with this problem too, they force the caches to get new files
Let me know if the problem persists.