Hi Scotty!  Mobile Me is telling me that I need to upgrade to the new calendar in order for my calendars to continue to sync, etc. and that the old calendar is expiring shortly.  I still have Leopard v 10.5 and it's saying that I need Snow Leopard v 10.6 in order to complete the upgrade for the new mobile me calendar.

Would you please fill me in here?  Do I need to move to Snow Leopard?  Thanks for your help!
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I've gotten this question several times.  Answers

You need to do this sooner or later.  You don't need to move to 10.6 to make it happen however. You just have to manually add the mobileme calendar into 10.5’s iCal.

First: backup iCal by going to File: Export: iCal archive or it may say “backup iCal”.

In iCal preferences go to accounts, click the plus to add an account.
description but “mobileme”.
username: your mobileme email address ie: sells@mac.com
password: your mobileme password

Then below that you’ll see a small triangle which toggles down to a field where you need to type the following: https://cal.me.com

Save those changes. Quit iCal and restart. You will now see a new set of calendars over to the left side of iCal. After all those download and you may have duplicates, you can then delete the prior calendars (usually listed above the new calendars) and you’re done.