Well I feel kind of dumb, I just purchased After Effects CS 5.5, and I already owned CS 5 Design Premium, so what happened was my CS 5.5 Extension Manager automaticaly opened when I tried to install the Fireworks CSS3 Mobile Pack, when I was about to do a screen shot, I noticed it. So, I simply opened the CS5 extension manager and it installed fine. Anyway, thanks for ypour help because I never would have noticed that. I am sure I am not the only one out there with two versions of extension manager. I appreciate your help, Dominic!
Please follow the below mentioned steps to install the Fireworks CSS3 Mobile Pack:
1) Manually launch CS5 Extension Manager.
2) Click on Install button in the Top Right side or Select the menu item File > Install Extension.
3) Browse and select the Fireworks CSS3 Mobile Pack extension and click Open.
Hope this solves your problem.