In the light of no other suggestions I'd try resetting prefs:
Hold down Ctrl+Alt+Shift (Windows) or Command+Option+Shift (Mac OS) immediately after you've clicked to launch the application.
You'll see a dialog asking if you want to reset prefs. Click OK.
You may have launched the AE rendering engine instead of the After Effects app.
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.