today a very strange feature arised in osx yosemite. Safari immediately quit after starting. In my system log files I found an error message regarding iCloud key Sync. The iCloud preferences pane quit with an error (known problem online). After searching a while I decided to open the disk utility and check the disk and the permissions. After a successful repair of the permissions and a restart the iCloud pane was working again, but another problem submerged. The fontd quit after starting and no fonts where found when launching the book app. All programs connecting to the fontd returned an error in the error log. Online there where no useful solutions to be found the only solution seems to be to restore the system. I found out that using the command „fontrestore default“ did the trick and after a reboot everything was fine again. I only had to check some fonts due to duplicates and that was it.
The system was very unresponsive during this problem. The applications stuck for minutes and so on just to have an anchorpoint for you. Check the console log and look for fontd crash reports as a sign regarding this behaviour.