Does your Avast detect FGunz as a virus ? If it does, no prob, follow these steps and i should fix that.
If your FGunz isn't working, and you have Avast, you should give this a try as well.
NOTE : THIS IS FOR AVAST USERS ONLY

1) Open up avast! On-Access Scanner using the icon on your task bar
http://i28.tinypic.com/hvqoi0.jpg
2) Click Details...>> for the extended view
http://i27.tinypic.com/21ah5sk.jpg
3) On the left, you should see a list of shields, scroll down until you see something called Standard Shield
http://i29.tinypic.com/9ld2s9.jpg
4) After clicking it, click Terminate and press Yes
http://i26.tinypic.com/2z8tb0m.jpg
5) Press OK and your done!
http://i32.tinypic.com/mr1uv.jpg
6) Start Gunz


If you have any questions, post em here. xD