Apple Mail View preferences aren't saved

Sheesh. What a day. I've spent much of it trying to get Apple Mail to sync properly with Gmail. Not entirely sure what got screwed up there, but it took a long time to sort out. I basically scrapped everything and then started again.

Much is working better now. However, I have encountered a new problem. Since I scrapped all the old preferences, I expected Mail to automatically create new preference files. I've customized the view a bit (turning off "Organize by conversation" in the View menu, and opting for Classic View in the preferences panel. However, when I quit and relaunch Mail, those preferences are gone -- reverting to the default.

Everything else is working normally. I've repaired permissions, and that didn't help.

Any thoughts??