Eric,
If you go into iCal, then Window > Address Panel or Command
OptionA brings it up.
There is always something I miss, or never noticed. 😉
Maybe it's supposed to be blank. EIther way, I have no idea what the point of it is. Is yours blank?
No, mine displays my Address Book entries.
It should not be blank. When I drag one of the entries to iCal it creates an event named "Meeting with..." (Name of contact).
...I think that might be the reason I can't invite attendees.
Perhaps refreshing the iCal plist file may return the function. You will find the com.apple.iCal.plist file in your Macintosh HD/Users/yourusername/Library/Preferences Folder. Quit iCal, drag the com.apple.iCal.plist file to your Desktop, log out/in or restart.
And yes, to upgrade the new MobileMe you go into the calendar section on MobileMe =).
I am waiting to upgrade when IOS 4.2 is released for the iPad.
;~)