I tried booting both x32 and x64 versions of ubuntu 12.04. When i choose Default/Try ubuntu without installing in the boot menu option, the system hangs and the booting stops.
Try to access a boot options screen. Most firmwares let you do this by pressing F2, F10, F12, or some other key at boot time. (Look for a prompt about this or consult your manual.) With any luck, you'll see two options for how to boot your CD, one in BIOS mode and one in EFI/UEFI mode. They aren't likely to be labelled this logically, though; you might see something like "Boot CD" and "Boot CD (UEFI shell)". Try both of those options. It's possible that your board is having problems with whichever mode it's selecting by default, but that the other one will work.