The link in your post inadvertently led me on to another guide where i found my solution to accessing x . Now Backtrack is installed and I could install the ATI CCC and drivers to solve the video issues at start-up.
The solution was so simple and just a something that i had skimmed over before.
In the grub menu press "TAB" to edit boot.
You will see something similar to "file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.gz text splash vga=791--"
Just add "xforcevesa" after "initrd.gz" and leaving "text splash vga=791--".
This worked for me! Although i'm not a hundred percent sure why haha.