That is a very common problem. You should look through the forum for help that has been posted time and time again.
One issue I believe is happening with many people is that EVE winds up installed mutliple times and there might be a conflict because of that. Have a look in your folders if you can (not familiar with Mac) and if there are multiple installs get rid of the extras and try to work with only one. If that does not work, you may need to get rid of them all and start over with a fresh install.
The problem with this is that you may lose window settings and need to rework them from within the game. You character information will be fine however if you just have your login credentials ready to enter manually. This includes a valid e-mail address.
Next, here is one of the many threads about this: Game won't start at all for me