It sounds like you changed the resolution settings to something larger than will fit on your screen, so the menu on the intro screen is too far down/right to be seen.
Resolution settings are stored in config.xml (in Username/Library/Application Support/FreeOrion/ ) and deleting and reinstalling the program won't remove that file; you'll need to delete it yourself, or edit it to set the resolution to what you want, if the in-game resolution selection isn't working for you. The relevant lines are (similar to)
Code:
<app-height>768</app-height>
<app-height-windowed>768</app-height-windowed>
<app-width>1024</app-width>
<app-width-windowed>1024</app-width-windowed>
.