it's stopping because you don't have catalyst 13.1 installed, not because it thinks you have 512MB of ram.
you may think you have it installed, but you don't. you're still using the old version. you need to completely remove the old version (with driver fusion if you're on windows) before installing the new version.
you may think you have it installed, but you don't. you're still using the old version. you need to completely remove the old version (with driver fusion if you're on windows) before installing the new version.