Well, I don't know if it'll help or not, but you can also go to Start> Search and click on All files and folders and type in either Gunz or Maiet and that should bring up all the files that have that name to it. Make sure that the files are related to Gunz so you don't accidentally delete something important.
If that doesn't work, check your firewall if you have one and make sure it's letting it download correctly, disable it if you have to. It could also be your hardware and stuff because I remember when I tried to play Counter-Strike: Source on my onboard video card, I got like 25-27 fps which is playable but a little choppy. Then when I uninstalled Counter-Strike: Source and installed it again I was getting around 7-9 fps which is absolutly horrible for gaming. Then I bought a RADEON 9700 Pro and a stick of 512 MB ram. The game runs really smooth with around 45 fps, (maybe just a little lower, but not much). Tell me what kind of video card you have because that possibly could be your problem. Write back again if you have another question.