Originally Posted by dgladst
If I interrupt the machine boot although it displays me a choice of operating system I am unable to select any of the options.
Can you explain (in detail) what you mean by this - exactly ?. How do you interrupt, what choices do you get, what do you choose ... ?.
Also, from a Ubuntu terminal, run these commands and post (all) the output
sudo fdisk -l you'll need to enter your password
grep -vE "(^#|^\s*$)" /boot/grub/menu.lst