OK, I dealt with the problem.
Here's the problem: XFree 4.3's driver 'nv' has issues with Riva TNT2 cards (at least those).
Solution: get into command line and install nVidia's latest driver, then edit the XF86Config files as explained in the nVidia install process.
Second problem: Redhat doesn't give you the choice to boot into command line.
Solution: I ended up installing Mandrake 9.1. :P