Right after upgrading my Macintosh laptop to Lion I found that iCal, the Mac calendar, was so slow. It was really aggravating. It happened with every change I made to my calendar. I guessed that the reason was my calendar was uploading to a remote server. I did have a .Mac account so I decided to look for this cause. I did find it to be the case.
- Open iCal preferences.
- Choose Accounts.
- If you see any listing showing “CalDav” select it.
- Select Account Information.
- Note the line listed as “Refresh Calendars:”
- I found this to be set as “Push”. THAT IS THE PROBLEM. Change it to anything else, but not “Push”. I chose every 15 minutes.
This completely solved the problem for me.