if startx will only give you a black screen with a white X for a cursor, try using kdm. this is the K desktop manager, which allows you to start up kde, should you have kde installed. if you use gnome, use gdm. if you dont have a desktop manager, i suggest getting one. personally i prefer KDE, but gnome is also available; along with blackbox, fluxbox, and TWN (tab window manager, which is a piece of crap).
edit: also, don't forget that you have the option of doing X -configure should you want to try and make X configure itself.
before copying over the new driver, i suggest backing up your current config by doing
mv /etc/X11/XF86Config /etc/X11/XF86Config-backup
hopefully this helps.