I haven't the window app.
You have; Mac OS Lion and Mt. Lion can have multiple Desktops, and sometimes it happens that an Application will open the windows on a different Desktop and you see nothing at all - just the empty Desktop. Mission Control will show you the other Desktops.
We really need a clue to what is going on to be able to help you. Are any error messages or diagnostics in the Console window? The Console Utility is in Applications > Utilities.
Look for any messages posted at the time Aperture is launching and post these messages please.
I have many filter for this app I can't change to lightroom..
What is the Aperture version you upgraded from? Aperture 3.3 or earlier? Then you may have plug-ins installed, that are no longer compatible with Aperture 3.4. Have you checked the plug-ins at the manufacturer's website, if they are the newest versions? You may need to update them.
Regards
Léonie