OK, let's try a few things and maybe we can pin this down in your case. First, we'll try getting rid of the prefs on your local machine.
First, open up the Corona Simulator. Open up "Preferences..." from the app's top menu, and click the "Deauthorize and Quit" button. This should take a few seconds, and the Simulator will then quit.
Also, make sure you don't have another version of the Simulator running. If so, do the same process for that. And, quit LuaGlider if you have that running.
Next, remove the Corona preference files. In the OS X Finder, click on your home directory (main user) to where you see the typical folders like Documents, Movies, Music, etc. Since OS X 10.7, Apple decided to "hide" the Library folder to discourage people getting in there and messing things up. So, now you have to access that by selecting (from the top menu) "Go > Go to Folder..." and then type in "~/library" and click Go. This should take you to the Library folder.
Once in there, open the "Application Support" folder. Locate both the "Corona" and "Corona Simulator" folders and trash them.
Now, back out to the main Library folder again, and locate/open the "Preferences" folder. If you see any files that start with "com.anscamobile.", please trash those. Also, look for the pair that starts with "com.coronalabs." and trash those.
Finally, log out from your account on the Corona website, restart the computer, and then try re-loading the Simulator. Please then report back what happens, and we'll go from there.