I know little about Sabayon, other than that it is based on Gentoo, and I don't use Fedora. However, your problems are quite probably the same as they would manifest on ANY linux distro.
As for refresh rate, I assume you are referring to the screen refresh rate, or maybe the frames-per-second rate. The place to investigate is which video driver you are using, and some other settings in your video config file, located at /etc/X11/xorg.conf.
Look for the 'Driver' line, which probably reads 'nv'. If you install the actual driver from nVidia.com, you will get much better video performance. As for the screen resolution and refresh rates, you need to look at your 'Screen' and 'DIsplay' sections or subsections, and make sure you have the resolution(s) you desire listed in there, and that your 'Monitor' section is configured properly with the correct scan and refresh rates, as per the specs of your monitor.
Now, as for the exact methods of installing the nvidia driver, should you choose to do so, I don't want to advise you, because again i don't use those distros. Generally the installer is run on its own from the console and takes care if the whole job all on its own, but I am aware that on Fedora, it can cause problems, so you ought to search around for some more accurate info on installing it into whichever distro you are using.
The nvidia website and also the driver itself, both have a very good README, and also, the man page for xorg.conf will be helpful to you.
Last edited by GrapefruiTgirl; 10-17-2007 at 07:20 PM.