Hi folks,
Took me a minute to work out how to do this, so here's my guide on it. The error message I was getting was "-bash: No such file or directory" when I tried to run a dynamically linked ELF executable (standard binary). Also, interestingly enough when I tried to "ldd" the executables, it was telling me that they were not dynamically linked, which I knew for a fact they were!
Really simply, Ubuntu 12.10 (Quantal Quetzal) x86_64 on Amazon EC2 doesn't come with any foreign architectures pre-installed.
To change this, it's a simple process of telling dpkg that it should also be looking for i386 as well as amd64 packages. The command is as follows:
sudo dpkg --add-architecture i386 && sudo apt-get update && sudo apt-get install ia32-libs
Bear in mind this guide is specific to Ubuntu 12.10. 12.04's dpkg won't understand --add-architecture. That notwithstanding, you should now happily be able to run x86 binaries on your x86_64 system without so much as a single reboot!
n00b