So fundamental to my use of iTunes and my iPod is the ability to transfer shuffled playlists over to my iPod, I have now managed to revert back to version 10.7.
It is by no means a straightforward thing to do, because Apple have made it difficult by apparently 'integrating iTunes within recent versions of OS X'. This in itself worries me, because it reeks of Microsoft policy...
Anyway, here's a guide to how to do it how I did. (Many thanks to other posters in other threads for the method; what I've tried to do here is provide a complete 'idiot's guide', which was what I really needed...)
First off, you will need a .dmg file of iTunes 10.7, which should still be available here:-
http://appldnld.apple.com/iTunes10/041-7195.20120912.d3uzQ/iTunes10.7.dmg
Download it and put it on your desktop, but DO NOT launch it yet.
Now, delete iTunes 11. This cannot be done, in Mountain Lion at least, in the usual way. You have to do it with the Terminal app.
Launch the Terminal app, (in Applications>Utilities), and type in the following at the command prompt:-
sudo rm -rf /applications/itunes.app
... and press Return. (Note the spaces, which are important... it's a bit like using the old Windows DOS thing.)
I ran into a snag here straight away, because it prompted me for my password, which at the time was blank, and it wouldn’t accept no password. So I assigned myself a new user password, (System Prefs>Users & Groups>Change Password), and it worked after that.
Note: After typing the command, exactly as above, nothing appears to happen. But if you look in Applications you will see that iTunes is no longer there.
Next double-click on the iTunes 10.7.dmg file that was previously downloaded, and install it as you would any other software by double-clicking the resulting disc image on the desktop and following the prompts.
It was at this stage that I found that, although I could now launch iTunes, and it was definitely 10.7 I was launching, the error message 'Error -42408' appeared every time I did so. I could live with that if it just meant getting the message, but I wasn’t sure whether everything 'under the bonnet' would work correctly as long as this error message was being generated. So I continued...
Close iTunes, if it is still running.
Next re-launch Terminal and type the following:-
open /system/library/privateframeworks
...and press Return.
Typing the above command in Terminal opens a new Finder window called 'Privateframeworks'. (Apparently one can only open this folder via Terminal; it is not visible using just Finder itself.)
Having done that, follow the following steps, one at a time. (I tried restoring all five files at once, but I was denied permission for some reason, so I did them separately.) Apologies if this is too basic...
The steps:-
First locate, in the 'Privateframeworks' Finder window, the file called 'AirTrafficHost.framework' and highlight it.
Next launch Time Machine, and wait for it to sort itself out. The 'Privateframeworks' Finder window remains visible, of course, in Time Machine, and the highlighted file also remains highlighted.
Now look back in Time Machine for a restore point in which the 'date modified' field for the highlighted file was a date well before you, ahem...'updated' iTunes to version 11. (In my case I chose a date in September.)
Click on the 'Restore' button on the right-hand side of the Time Machine bottom bar.
When prompted, select the option to 'Replace' the existing version of the file with the one you are restoring. Also, enter your password when prompted, of course.
With the 'Privateframeworks' finder window still open on your desktop, locate the file within it called 'CoreFP.framework' and highlight it, launch Time Machine as before and restore that file the same way as the first.
Next, locate the file called 'DeviceLink.framework', highlight it and follow the same procedure with Time Machine to restore that.
Do the same thing with two more files in the 'Privateframeworks' finder window, called 'iTunesAccess.framework' and 'MobileDevice.framework'.
Close the 'Privateframeworks' finder window and quit Terminal. (I think I could have quit Terminal as soon as I'd opened the finder window though, to be honest.)
And after doing all that iTunes 10.7 should launch happily without the error message. Bliss...!