So, a month after starting this thread, I still don't have a working iCloud setup. I've checked everything that's been recommended, and everything else I can find, with no success. Here are my vitals:
iMac running 10.7.2
iPad 2 running 5.0.1
iPhone 4 running 5.0.1
I'm primarily interested in having my calendars and contacts in sync with each other. I've checked the "Calendars" button on each device and made sure they were all set to "all" (they were). I do most, but not all, of my calendar entries on the iMac, and the two mobile devices haven't gotten any of the appointments I've entered there. I just checked the iCloud settings in my iMac System Preferences and they're set to sync Calendars and Contacts, which is all I really care about.
I'm using 1.8 GB of iCloud storage, for what it's worth.
I'd love to get iCloud working on my computer - any suggestions?
Gary