For a very long time I found that my iCal was unusable.  Every time I opened it up I would get the spinning color wheel of death.  Because Apple shut down mobile me and they threw up a splash screen on my Control Panel that said “MobileMe Sync has been disabled because an iCloud account is active.  Use Mail, Contacts, & Calendars to manage Sync”.  I have an iPad and wanted my Mac laptop to be synchronized to it.  I had to now troubleshoot the iCal problem.  Here are some bullet points that may work for you if you have the iCal spinning wheel of death problem.

Target device: Mac computer, either laptop or tower.
Cause of the spinning wheel of death:  Duplicate calendar items.  We are looking at possibly thousands of duplicates.  I found I had over ten thousand duplicates of the same items!
Culprit: Entourage.  This solution is only for those users that synchronize Entourage with their Apple computers. Second problem may be having too many calendars.
Improvement:  Before the delete of duplicates, the program would NOT successfully load.  After delete of duplicates, 2 minutes and 15 seconds to load.

Primary method to resolve this problem:

Warning: Many of the process items may take a very long time to complete because your Mac computer will show you the spinning wheel for tasks even outside of iCal.  When you begin to fix iCal the program may be so slow to respond because it is struggling so hard.  You may be waiting a long time to complete some of these tasks.

Turn off all synchronization between your computer and iCloud.  We do not want any device to rewrite into the computer when we do a delete of the duplicate items in Entourage.  Go to your computer System Preferences and then select MoblieMe to open that window up and lets see what you have.  You should see the long button “Mail, Contacts & Calendars” click on it to open that selection.  That button can be found by choosing, first, “Sync” or “Back to My Mac”.  On the left side column of accounts, select “iCloud”.  Next turn off the check box for Calendars that shows on the center and right part of the display screen.  Look at each and every e-mail account.  Some come with calendars option.  Try turning off all calendars for now.  You can turn them off later.  Just keep a list of mail programs that also come with calendars and write them down and whether you shut that feature off and I hope you did so for this exercise.

Here is a list of e-mail accounts that I found came with “Calendars”:

• iCloud
• State university using Entourage
• G-mail
• Rocketmail.com
• Yahoo Mail

Turn each one off by un-checking the check box.  Make a note as to the ones you turn off as you may wish to turn them back on later.

Now open your computer Entourage application.  Under “Calendar Views” choose “All Events”.  If you see an extremely long list of duplicates, then you should seriously consider deleting them.  I had so many, it took me hours to get rid of them.  I had to use the mouse select first item and shift select the second item to delete bunches of duplicates.

Second method used:

The next method I used was to delete all the calendars that were no longer necessary.  I had calendars that I could not remember ever creating.  I found these major categories of calendars:

•     On My Mac
•     iCloud?    Rocketmail.com
•     Gmail
•     Delegates
•     Subscriptions

Method:  We need to first lessen the processing load for the iCal program by unchecking calendars and deleting those checked or unchecked that are not needed.  Do not delete any calendar that you need, only calendars that are not necessary.    The process is simple.  Just right mouse click on a calendar you wish to delete and you then may have to wait quite a long time for a response to show up on your computer screen offering the choice to delete that calendar.

A really disturbing event took place.  I deleted a whole bunch of calendars and the next day they appeared again from iCloud.  This means that some device somewhere, was sending those calendars up to the Cloud.  This is when I discovered that some of the mail accounts came with their own calendars and I had to go back in and turn them off.

An interesting benefit in cleaning this problem up was that before I did the deletes of duplicates, Entourage would take forever to complete its load.  The program now loads about one third quicker.