I have a Diamond Viper V330 AGP card and Red Hat Linux 7 is booting to a non-viewable screen during the installation process. Right after it tries to "jump" to graphics mode for the first time (after verifying/detecting misc. devices), The screen looks like 4-5 interlaced images, slightly shifted relative to each other. It is like it is trying to set a graphics mode that the card cannot handle.
I believe this problem is fixed in our latest Rawhide release. Please upgrade to the latest XFree86-4.0.3 and Mesa 3.4-13 located at: ftp://people.redhat.com/mharris It should work for you I believe. If not, please reopen the bug.