Try going into your time a date through the system preferences and see if it still freezes up that way. Also checks for system OS updates. Are you on 10.7 or 10.6 or one of the more outdated OS's? The time at the top right is probably set to update from apple. If you do get into your time and date setting you can always switch it to manual. This happens quite a bit so going with manual might not be all that bad of an idea. The time in your dashboard is set to a different source.