It's turned on in .htaccess - I got the warning about register globals when I first ran the install script. I made the entry in .htaccess and then the install script no longer complained...
Maybe .htaccess is in the wrong directory, affecting only installation files? Does it affect a whole directory tree recursively? You may include some phpinfo() inside the php files to make sure what is the value of register at run time.
On the client side, did you try with different browsers? Sorry i have more questions than answers, just trying to help.
