Is it possible that you have accidently deleted the folder called p_drive? If so, just create a folder called p_drive under EVE Online Preferences. If you haven't touched these folders try following the instructions given in this post: http://myeve.eve-online.com/ingameboard.asp?a=topic&threadID=651579&page=1#3
This is what it should look like:
Library\Preferences\EVE Online Preferences\p_drive\Local Settings\application Data\CCP\EVE
If you are missing any of these folders, just create a new one and name it with the exact same name and try to launch the game again.