If i click on the unity dock icon it does not open. i had to set it to open at login. now the only time it will start up is when i restart my computer. why is this? someone save me!!! Please. 
- try reinstalling Unity
- The osx updates sometimes screw it up.
Browse the forum for the word crash and youll find how others get round it
incidentally are you using a server setup at all? We had this behaviour at school, creating a new user with access to the local drive and unplugging netwaok cable on login was an effective workaround.
Good luck
AC
Sometimes my projects get junked up or I do Something Bad and they won’t start. I try to keep a simple scene in the same project as the complex one, and if it breaks I’ll navigate to and open the simple scene, and it will open and fix the linkages in the project, and allow the complex scene to open again. Maybe.
Also try restarting Unity while holding down the Option key, then open a different project or creating a new one. Perhaps the last project you had open is causing some weird crash (Unity opens your last project by default).