Hello, I had the same Problem whith my ASUS card (RIVA TNT 2 based).
First make sure the modules are correctly loaded. You have to change your modelines. Make sure all your modelines are commented out. Try to first use the default-modes. Enter them as a mode for your device eg. "1024x768". This mode shouldn't have a modeline. Now X should be able to start. If not try using other modes. To get back your old refresh rate run xvidtune. Use the "show" button to show the current modeline. Put the values of the output into your XF86Config-4 at the old modeline for this resolution. Do NOT overwrite the first and second value of your old modeline! Now you should have a Mode in your prefered refresh rate. Adjust your monitor by hand not using xdvitune. Hope this helps Bye -- Bastian Bowe
