I have just downloaded Xcode off the App Store and now when I try to open it I get this error:
The application "AppDownloadLauncher" is not open anymore.
What does this mean and how do I open Xcode?
The process AppDownloadLauncher is used to launch apps from the Mac App Store. The error is shown when a problem occurred communicating with this process.
Use Activity Monitor to force quit AppDownloadLauncher, then try relaunching Xcode.
If this doesn't help, log out and back in.