well i have an intell mac mini and i had ubuntu 11.04 32 bit running on it just fine but now i want 64 bit so i made an install disk but when i boot to it i get my grub list of try ubuntu, install, or check if disk is bad. well heres my problem, i try every one of them and they dont work, i think its the try ubuntu that just leaves a blinking underascore on the screen but the other 2 leave a black screen, can anyone help me???