I don't really know, but it would be well worth looking on the web for it... google can find most things like this.
Also remember that it could be your monitor, not your video card. If Red Hat detected it as something it's not and tried to give it a refresh rate or resolution that the monitor couldn't handle then a blank screen may indeed be all you get.
So I'd say it is either the above or the S3 drivers.
It might be handy/necessary to edit the file /etc/X11/XF86Config-4 (Red Hat installs XFree86 v.4 by default, so don't get mixed up with the file /etc/X11/XF86Config). This file has all the X configuration in it, including what drivers to load, what monitors are available, in what resolutions, etc...
It'd be best to look around on the net for more info first, but chances are if you find an answer, it will involve messgin around with that file.
Sorry I can't be more specific about your problem, my last S3 card was in a 486-40