I'm having the same problem as well. See this thread https://discussions.apple.com/message/19929421#19929421
Were you ever able to come up with a fix for this? It sounds like problems at Apple's end, but it is very frustrating nevertheless since it is critical that I be able to see my wife's shared calendars with the amount of time we spend apart traveling.
Many thanks in advance for your help.
Erik Lars Hansen
Finally, success. Some time today Calendar.app on my iMac started working properly again. My wife's shared calendar events are showing up, the program no longer hangs with the error message "can't connect to P02.caldav.icloud.com...", events created on Calendar.app upload to iCloud.com and then out to my iOS devices as well. I wish I knew what had been done by the iCloud engineers to make this work, but I'm happy that I finally have a working calendar back together. I have just sent an email to the senior Apple tech who has been my contact through this asking him if he could provide me with any additional information on what fixed the problem, and if I learn anything more, I'll post it.