To boot in text mode, when grub comes up, don't just boot as normal. Instead press 'e' to edit your normal boot option. Simply add the number '3' to the line that begins 'kernel ...'. This only affects the current boot, but once you've got into Linux, you can modify the inittab again.
I'm not familiar with the video card, but you could try switching to the vesa drivers for the time being. Open up /etc/X11/xorg.conf and find the section relating to the graphics card. It should be clearly marked as such. In that section there will be a line that begins 'Driver ...'. Comment this line out (put a '#' at the beginning) and add a new line as follows:
Save the file and try starting x with the command 'startx'. Hopefully it works, in which case you can switch the default runlevel back to 5. If it doesn't work, you can get back to the command line by pressing Ctrl-Alt-Backspace. Assuming it does work, you can then hunt around to see if you can get the proper driver working.
Good luck!