me.com or mac.com?

Have you attempted using your regular Apple ID? I believe they both are interchangeable.

The preference pane was removed, you just haven't updated yet! That could be the source of some confusion for you.

yourname@mac.com and yourname@me.com are theoretically completely interchangeable though a few people have commented about one working when the other didn't.

Back To My Mac still works: you have to turn it on in System Preferences>iCloud

http://support.apple.com/kb/PH2572

The MobileMe preference pane has been removed in Mountain Lion.

They may be theoreticall interchangeable but the problems I'm getting seem to be linked to the difference that perhaps still exists between them. In MAIL I can choose my alias for iCloud. In iCal I can't. One has the address ending in mac.com, the other in me.com. My iCal has gone completely haywire and I can't even restore it from old backups in Time Machine. I'm wondering whether this is because at some point - presumably the moment when the whole thing went pear-shaped - the old data was left on mac.com and I can't access that because my iCal only produces calendars that are linked to me.com, so the data that I import has nowhere to go. Is that silly? I would greatly appreciate any help I can get as my only prospect now is to re-enter thousands of events and even if I do that I have no confidence that they will not disappear all over again. I suppose the other option is to never use iCal again and I'll consider that if there's no better way.

As long as the part before the @ is the same, @mac.com and @me.com are the same thing and are interchangeable. Of course if you have something different before the @ then there are two separate accounts and you can't sync between them. You would need to transfer data from one to the other.

There is no difference between the pre-@ parts of the two addresses.The situation is that a month ago my iCal went crazy. For a while, under the guidance of other forum posters, I managed to restore the previous calendars. Over time, they became more and more crazy until now I have only very recent events listed and none of the thousands of events that had been there before. Now I can't restore anything, using Time Machine or even icbu calendars I've saved to the desktop. I go into Time Machine and try to restore old calendars, even extremely old calendars that existed long before the problems I'm having and nothing works. I suspect that I will have to forget about using iCal and find another calendat application. I wish it wasn't so but can anyone suggest a better idea?

If an iCloud calendar has been deleted and you restore it from a backup, it will promptly be deleted again as iCloud's syncing system will helpfully bring it into line with what it sees as current reality.

You can get round it, but it's a bit of a fandango, described in this page:

Restoring iCloud calendars from Time Machine or other backup

If you still can't get it sorted I should ask in the iCal forum.

I've resorted to the fandango several times without success and I've posted several cries for help in the iCal forum without receiving any responses. The most mystifying thing at the moment is that restoring old calendar files from Time Machine doesn't bring back the old list of events, even temporarily. How can this be?

Dear Roger, thanks for your help. In fact I hadn't tried your fandango, but another one somewhat like it. Where I come to grief is in identifying the various .ics files that are within the events folder of the calendars folder. Inside the calendars folder it looks like this:

file://localhost/Users/peterbest1/Library/Calendars/4ECD0D38-97CC-4EF7-BB81-8C56 672F72D0.caldav/

file://localhost/Users/peterbest1/Library/Calendars/30750D28-1CDF-4785-BBEA-0569 EC657EE2.calendar/

file://localhost/Users/peterbest1/Library/Calendars/Calendar%20Cache

file://localhost/Users/peterbest1/Library/Calendars/Calendar%20Cache~

file://localhost/Users/peterbest1/Library/Calendars/Calendar%20Sync%20Changes/

file://localhost/Users/peterbest1/Library/Calendars/DD743D51-8AD6-4FEE-AB0B-1F63 38B443FE.calendar/

file://localhost/Users/peterbest1/Library/Calendars/Email%20Cache.plist

file://localhost/Users/peterbest1/Library/Calendars/Incoming/

If I choose one of the folders ending in .calendar/ or in .caldav/ I get further folders, in each of which, in the events folder, I get dozens, maybe hundreds of .ics files, each one from a different date. How do I know which of the files to import, or do I have to import each of them? And how can I determine which of the folders ending in .calendar/ applies to which calendar? There are currently 2 iCloud calendars. Which of them do I restore from the .caldav/ folder, which itself contains further folders? It's so bewildering I want to scream. Perhaps I should just pay to go to the genius bar with my iMac and Time Machine drive and hope that somebody there will know what to do?

Have a look at this site which walks you through a method which worked for the author.

http://chasingaftermoonbeams.blogspot.co.uk/2012/05/restoring-lost-ical-events-a nd.html

Please note that I post this for information: I've not tried this and I know nothing about the author. Back up what you have now before you start attempting this.

Dear Roger, this worked. I didn't think it had, as everything disappeared when iCloud swung its usual right hook, but later it came back. The difference between this advice and everything else I've read (and I've read a lot) is that it gets rid of everything to do with iCal from my iMac, so the restoring process from Time Machine is complete. Why that then manages to fool iCloud I don't know, but somehow it did and all is well. Thank you very much.