iCAL no funciona

Gracias Sprad: contesto tus preguntas:

1) los updates están instalados
2) no sé como se repara "permissions"
3) cambio de usuario y abre OK
4) borro las preferencias del iCal pero sigue sin funcionar.

alguna sugerencia mas?

para reparar permisos o permissions (segun el idioma) hay que ir a Disco duro > Applications > Utilities > Disk Utility, seleccionar nuestro disco duro y hacer click en "Repair permissions", va a tardar unos minutos... simple as that

Google al rescate!

Anda a tuuser/Library/Calendars y borra el o los "Calendar Cache".
Ahora tendria que andar

Si sigue sin funccionar te hago un copy paste:
1) repair permission by going to applications/utilities/disk utility and repair permissions, after that is done, can you open ical?
1) go to the homefolder/library/calendars and for that folder get info, see if you are set as a user on that folder, and if so, what rights you have, read only? if so then change to read and write. do the same with homefolder/library/application support/ical. does that clear up the issue?
1) log in as a different user - create a test user for example - and see if you can try to open ical. let me know if you can
2) in your normal user account, back up the calendars folder in homefolder/library/, and also back up the folder ical in homefolder/library/application support/ ,say make a copy and keep on an external hard drive
3) go to the homefolder /library and drag the contents of the calendar folder to the desktop, now try to open ical?
4) have you synced ical calendars in the past, if so try to reset sync history in isync>preferences, does it help
Source: http://discussions.Apple.com/thread.jspa?messageID=6643688