Since Migration Assistant blew up while moving to my new Mac, I've had continuing problems with permissions throughout the system.
I believe the problem is that the Apps can't save into my Library. I have only two permissions across my entire Home folder tree, me read-write and everyone read-only. I seem to be the owner for every file.
Can someone out there poke about in their Library and similar folders and see if this is the same? I suspect that either a group needs write permission, or that some of the files are not supposed to be owned by me.
Best Answer
Ok, just in case this comes up again, maybe I'll find my own answer :-)
The problem is that modern versions of OS X apply new permissions seemingly at random when problems are encountered. In this case, the OS added a third permission to everything below the home folder, and the permission was "everyone (custom)". Opening it, I found it disallowed writes by me to my own folder.
Suggestions for others; pick a file at random, maybe in your documents, and Get Info. Look at permissions - the first line should be "me", and is likely broken otherwise. Also check the enclosing folder for same.