How to get iCal in 10.5.8 back to syncing after the mobileme upgrade:

Go to iCal’s preferences.
Now select accounts
Now add account by clicking the plus button in the bottom left corner.
Now enter mobileme for the name of the account
enter your full mobileme email address and password

Now for the trick part, select the toggle triangle in server and enter the following: https:/cal.me.com

Your mobileme calendars should appear in the left hand column. Hope that worked.