I had sort of the same problem... But I'm using a different video card....
What I did to be able to change the configuration for X until I had it right is:
1 I boot up with the 2 instalation disks you created to install 1.9
2 Instead of doing the instalation, once the menues come up, I mounted the previousle initialized partition of my hardrive...
3 Opne a Shell, is one of the last options in the menu... This let's you then do a cd /target (wich is your hard drive)
4 Look for the file /etc.init.d/gdm and edit it (the shell has a very simple editor to use editor called ae)... So run ae /target/etc/init.d/gdm and put an exti 0 line at the begginig of the file... Save it... This will prevent linux from starting in graphics mode...
4 When you reboot you can login as root, run adminmenu, and reconfigure X until you get it right...
Hope this helps!