When trying install Ubuntu on Zenbook UX21 I always get same problem - after choosing installing Ubuntu, screen become black and installation doesnt progress. Any hint?
You could try passing some options to the installer and seeing if this gets you a display.
Look at the "F6" options. You can in particular try noapic and nomodeset, they may help on your system.
Alternatively, you could try the "alternate" installer, it has a better chance of working if the problem with your system is display-related. Be warned, however, that the alternate installer is text-based and is a bit more difficult to use than the standard installation. Get the alternate CD here:
choose ubuntu-11.10-alternate-i386 (or amd64, depending on whether your system supports 64-bit or not).