I just installed Leopard successfully, yet iChat, iCal and Address Book stopped working. Every time I click on iCal it quits unexpectedly. I've tried relaunching, resetting and relaunching but it won't open.
I found the issue (at least on my computer), the links in my doc weren't updated. They were trying to open the old version of iCal. I deleted iCal, iChat, & Address Book from my dock and the associated old apps (i had them in a subfolder). Now when I open iCal from the Applications folder it works fine.