Check menu-->settings-->Session and Startup
and see if there is anything for thunar in applications autostart tab.
Excellent suggestions. "file manager" was checked to autostart. When I edited "file manager" it said "command: Thunar."
I changed it to "command: pcmanfm" and strongly suspect that will fix my problem. Still something of a mystery why Thunar would run at all. I checked gslapt just now and there is no thunar listed. Just thunar-volman and ucastall. Don't see a "thunar" per se. I have testing repository enabled.
Anyway, thanks for the suggestions. They worked.