Hello,
I found out a solution... Log out of all things on ROBLOX.
Shut Down Your Computer Properly. Then Remove all devices from the computer
Ex. headphones, USB drives, Game Discs... Speakers if possible.
Wait about 1 Hour before turning on your computer... WAIT FOR THE COMPUTER TO FULLY LOAD... Wait 5 Minutes before opening anything on the computer.... After 5 minutes... Plug the devices back in slowly.
Then go to http://www.roblox.com/Install/Download.aspx
Click only one time... Uncheck "Warn all the time" Then click Run.