How are you seeing that it's opening and then closing -- viewing active processes, or does the actual GUI display and then disappear? If it's the former, it could be because a LimeWire is already running (and tells the second one to quit) -- check the system tray for a LimeWire icon, or go to Tools -> Options, Shutdown and tell LimeWire to shut down immediately. If it's the latter, I'm not sure what's wrong.