Well, no I don't think I have a disk corruption problem. I think the SQL database got corrupted, probably by a reboot or something. I found this post that seemed promising, but in my case did not work.

http://techblog.dorogin.com/2011/05/...-image-is.html

I tried following the suggestion on the last comment. I used SqliteBrowser to open the database and dump it as a new one. Some errors were reported saying that some records were not unique, but it created the file OK. The resulting file was slightly smaller than the original. I overwrote the one on the phone and rebooted. Upon reboot, my backgounds were gone. The phone booted into portrait mode but returned to landscape after opening the Programs Menu. (I first noticed his behavior after the last CSSU update so that is my prime suspect for this problem.)

Unfortunately the phone and conversation apps are still the same. I think I am just going to restore from backup. (I am going to have a coffee first, to calm my frustration.)