Does your AVG detect FGunz as a virus ? If it does, no prob, follow these steps and i should fix that.
EDIT : If your FGunz isn't working, and you have AVG, you should give this a try as well.
NOTE : THIS IS FOR AVG USERS ONLY
1) Open up AVG using the icon on your taskbar
http://i32.tinypic.com/2465s37.jpg
2) Click Components and click Resident Shield
http://i28.tinypic.com/2cz54es.jpg
3) Click Manage Acceptions [Another window will pop up]
http://i28.tinypic.com/24zwtjk.jpg
4) Click Add Path and look for your FGunz folder
http://i31.tinypic.com/291hjs9.jpg
5) Select your FGunz folder and click OK, and OK again.
http://i25.tinypic.com/smf31j.jpg
6) Click Save Changes, and yoru done !
http://i29.tinypic.com/2ltrccz.jpg
7) Run FGunz, it should work fine now
If you have any questions, post em here. xD