My problem was not with combat arms. There was no need to reinstall the game for me. Somebody played a lil joke and put my name under restrictions. If you have different log-in accounts for windows, check with the admistrator to make sure they didnt restrict you. I found this was my problem only after 3 hrs of trying to work with it. Not funny at all.
If you download the set-up and have it saved, I would just use that same set-up file that you used before. Be sure to clear out the nexon folder completly before try to reinstall